"Popping" noise when starting

[jsmeltser]

I have a 2008 GZ250 that I've put 3500 miles on this summer. Lately, when I start from a cold start there is a loud popping noise that seems to come from the front of the bike and then when I give the bike gas I get the same sound until it warms up. Sorry I can't describe this any better. I'm going to take the bike in for the 3000 mile service but my local dealer is a complete douche so I'm not terribly confident with them. Any ideas?

[Easy Rider]

I have a 2008 GZ250 that I've put 3500 miles on this summer. Lately, when I start from a cold start there is a loud popping noise that seems to come from the front of the bike and then when I give the bike gas I get the same sound until it warms up.

Could it be just the pipes heating up and expanding? Hope so.
If that's what it is, your header bolts might be a little loose.
If you check them, be careful; they should just be snug, not TIGHT.

[jsmeltser]

That was my first thought as well. I tightened them up a bit and the sound did seem to go away for a day or two, but it's back now. I'll report back after the service...

[El Diablo]

Is it popping or pootting. Could it be coming from your carburetor. My old Yamaha 350 Big Bear will get out of kilter every once in a while and will register a loud poot, kind of like a back fire, only it is more like a front fire.

[jsmeltser]

lol, I'm not sure if it's a 'poot' or a pop, but I definitely describe it as a 'front-fire'.

[Easy Rider]

lol, I'm not sure if it's a 'poot' or a pop, but I definitely describe it as a 'front-fire'.

I just don't know about you young rookies........... :)
A real back fire comes BACK through the carb. That is why it is called a BACK fire.
What is now commonly called a backfire really isn't; it is an AFTER fire.....in the exhaust system.

EDIT: OK, that really isn't right either. One just needs to distinguish between an exhaust backfire and an intake backfire......which has all but disappeared with widespread use of fuel injection.

Brought to you by a charter member of the old farts club ! :crackup

[patrick_777]

Brought to you by a charter member of the old farts club ! :crackup

Thus, he is VERY familiar with things that make "poot" sounds.

[Easy Rider]

[quote="Easy Rider":yn9k0031]Brought to you by a charter member of the old farts club ! :crackup

Thus, he is VERY familiar with things that make "poot" sounds.[/quote:yn9k0031]

:shocked: :neener: :skull:

[Quimrider]

My 2000 with just under 10,000 miles makes a poot from the front of the engine when I start. The head gasket appears to have developed a leak. It is a very unusual sound. It has been doing it for a while, I just ignored it. Last Friday when leaving work. I noticed a small puff of smoke accompanied the sound from the front of the engine. It took what seemed like a dozen restarts to figure out where it was coming from. That could be the prob. but I would doubt it on such a new bike.

[jsmeltser]

Well I've FINALLY got my service scheduled, so hopefully the mystery of the poot will come to a close. ;)

[jsmeltser]

Just got the bike out of storage and took it to a different dealer. The mystery of the pop/poot is solved. Quimrider was actually dead on, the head gasket was completely blown. It seems that the nut that holds it together had managed to work it's way completely off. Luckily the bike is still under warranty, so the repair was free. The guy who did the work said that it must be a known issue, because Suzuki sent a sort of locknut that he hadn't seen before, and asked him about my height/weight.

Sooooo glad that the cold weather appears to finally be over and I can get back on two wheels!!!

[Quimrider]

Glad you got it fixed under warranty! My fix cost me $330. The mechanic said that my head had slightly warped so they machined it down a very small amount. Hopefully they checked to see if yours had warped too. I'm 5'10" 200lbs and I rode about 50/50 freeway/city streets with a 16t front sprocket. If you don't mind me asking what are your riding habbits? I now ride a Vulcan 500 since I plan on making some long dist freeway trips this summer. I really want to keep my GZ, but i just can't justify the insurance/license plates for both :(

[jsmeltser]

I'm 5'9" 180 lbs. I ride about 80/20 highway/in-town. With all of the highway riding I do, I feel like I'm really pushing the limits of the GZ. I was actually planning on getting a Triumph this summer and passing the GZ on to my wife, but we had a very expensive emergency, so I'll be avoiding the freeway for awhile yet.

[wdnavion]

Popping noise when starting...I had this problem at about 25,000 miles..The head gasket layers were split apart at the left front and that was the causing the leakage. When I retorqued the large nuts on the cylinder studs...(27.5 foot lbs), the left front nut was loose. When I retorqued the small front hold down nut (underneath...the one that takes the 10 mm wrench), it would not tighten..just kept turning and I could tell that the stud was pulling out of the cylinder head...so I ordered the cylinder head gasket, the two copper gaskets, another stud (M6), and bought an M6-1 helicoil kit at the local AutoZone. You download the excellent GZ250 Service manual from this site and remove the valve cover, follow the instructions to remove the head which entails removing the camshaft, and get the cylinder head out on the bench. Remove the stud, carefully enlarge the hole with a 1/4 inch bit, being careful to not deepen the hole. Use the tap included with the helicoil kit, follow the instructions to turn in the insert and break the tang. Install the new stud with loctite making sure it is fairly tight in the insert. I would recommend not removing the cylinder until you get to the point where you need new piston rings which should be over 50,000 miles unless you are one of the rare folks who forget to change engine oil...

[wdnavion]

More Pictures

[wdnavion]

Yet another couple of Pix

[wdnavion]

Oops!

[jsmeltser]

Thanks for the info guys. Unfortunately this is an ongoing issue. About a month after having the head gasket replaced, the 10mm nut had worked its way loose again. The dealership mechanic put it back in and used loctite. After this I was a little paranoid about that stud and checked it before each ride. Sure enough, two weeks later, it was out again! The bike has been at the dealership for two weeks now. Had the head machined and they are replacing the gasket again. Currently waiting on the stud, which is on backorder...I can't imagine why! Luckily Suzuki is paying for the work again, even though the warranty ran out two weeks prior to this last incident.

[wdnavion]

Mr. Smeltser,
This does sound like the same issue that I addressed in the earlier post from yesterday. The GZ250 is not liquid cooled and when it is ridden fast and hard in hot weather, the head material around the exhaust valves gets pretty darned hot. Lugging the engine i.e. running in a higher gear at lower RPM at high throttle settings exacerbates this high temperature situation. Also lots of almost WOT operation at near top speed especially on very hot days hastens the issue. This causes the aluminum head to expand between the cylinder and the big stud nuts. This results in a lot of pressure on the head gasket. The repeated thermal cycling which results from going to cool to hot and back again eventually results in compression of the head gasket...it actually gets a little thinner and then allows the leakage to start. When the gasket first starts to fail, it is only noticed when the engine is cold at startup and then symptoms go away as the engine warms up. If you are having an ongoing issue with head gasket failure, I suggest my previous post concerning installing the M6 "helicoil" threaded insert in the hole for the front cylinder stud. This provides a much stronger mounting for the stud than the original fine threads in soft aluminum situation. It is important to do a good job with drilling and tapping this hole so that you do not have problems later. Because the insert kits run about $30 to $40, you can probably take the head to a reputable machine shop and have the whole thing done right for not much more than the ridiculous price of the insert kit at the local car parts shop! And no, you do not have to use loctite on a permanent "helicoil" repair...that is just something I do but not a normal or necessary thing. Now, on to my second suggestion, I highly recommend that you use a special sealant on the head gasket when you put it back together. It is called Hylomar Advanced Formulation Gasket & Jointing Compound. You will probably not find it at run of the mil car parts shops but it is available from engine rebuilding suppliers. If you have problems finding it, call a local engine rebuilder to see if they can get it for you. When you put the cylinder head back on, ensure that the parting surfaces are absolutely clean and dry and free of oily residue. Take a plastic spatula or small plastic scraper and carefully "squeegee" a thin film of the compound onto both sides of the new head gasket. When you reinstall the head, make sure that you do not over-torque the heads beyond 28 foot pounds because all you are doing is crushing the new gasket and reducing its resistance to thermal cycling. You can also use the Hylomar compound on the valve cover..just make sure that you clean any oil from the parting surfaces and use just a thin coating. I hope this helps.....

[Water Warrior 2]

Excellant pics and info. Could this be made into a "Sticky" for future reference ??

[johnd]

The "popping" blown head gasket pictures and instructions. This may be a dumb question considering the GZ250 is what it is. But when you remove the head and the timing chain can you get the engine out of time? I have an old Gaveley Tractor and if you remove and reinstall the magneto you have to be careful as if will be (I think) 180 degrees off and will not fire for love nor money.

Mr. Wdnavion: Is you name somehow related to those wonderful Ryan Navion Airplanes from the late forties?

Thanks,
John D

[Quimrider]

Not a complete answer since I'm no GZ250 engine expert, just my 2cents. Spark timing is off the magnito/alternator, so spark timing wouldn't be affected. I could see where your valve timing would get off if you don't get the cam put back in with the same position it was taken out or if you moved the crank shaft at all.

[Water Warrior 2]

Mark as many parts as possible before and during disassembly. Take pics during all the work. Make notes and read them over and over. OR, just be like me with a box of parts and wondering Why it won't work.

[jsmeltser]

I hate it when I have a box of parts and no idea how to get them back together! I'm not the most mechanically inclined guy around. :)

[wdnavion]

Yes JohnD, we have a 49 Navion which I can't afford to fly just now but it is a wonderful machine.
As to "getting out of time", it is not a big problem. You remove the plug from the alternator side of the engine case and bump the machine in high gear until the "T" mark on the alternator rotor inside lines up in the center of the plug hole. It should have a dab of gray paint from the factory to make it easier to find. Just make sure that you have the rotor in that position when you re-install the camshaft in the head. Make sure that you have the punch mark with the white paint on the camshaft pointing aft and aligned with the parting surface for the valve cover. You do want to make sure that both valves are closed when you remove the valve cover. The difficult part of the job is that there is just barely enough room to get the valve cover on and off the head since it is so close to the frame tube under the fuel tank. Also, in order to get the chain off the sprocket to remove the head, you have to take the two bolts off and remove the sprocket and then the camshaft. It is fun being careful to not drop the bolts and the keeper retainer from falling down into the crankcase where they might be hard to retrieve even with a magnet. Also use tywraps as in the pictures to keep the chain from falling down into the crankcase. It took me about 5 hours from start to finish including inserting the helicoil. The instructions in the factory manual found on this web site was pretty thorough.

[wdnavion]

I am adding this to help (I hope) reduce some confusion in performing the head gasket replacement procedure...

As I stated in the forum, there is not a lot of room between the top member of the frame and the top of the valve cover. If I were going remove the cylinder head again, I would probably use some thin wire ties or possibly some plastic tape to get the wiring harness up on the side of the frame member to get a little more clearance. I think I stated that you want all the valves to be closed when you remove or install the valve cover. This is because the valve springs will push the valve cover up making it difficult to remove and next to impossible to re-install. So the easy way to know that the valves are closed is to remove the spark plug and put the bike in a higher gear and put your finger over the spark plug hole. Slowly push the bike forward until you feel the air pushing out. When you feel the pressure dropping that means that you are at near top dead center and the valves will all be closed. Then you can remove the valve cover. Once you have removed the cover, it is a good time to establish the timing marks so that you will have confidence that you are getting them right when you put the engine back together. Remove the threaded plug in the top of the left hand engine case. Use a flashlight if necessary, but look straight down into the hole as you rotate the engine forward...again you can slowly push the bike forward in 4th or 5th gear until the T mark with the gray paint (in my 2002 bike anyway) is centered in the hole. At that time, if you view the camshaft sprocket from the right hand side, you should have the scribed and white painted mark at precisely the 9:00 position...

Moving on to removing the head, remember that you have to remove the four bolts which mount the exhaust pipe collars. Once you have done that, you will most likely find that you have to remove the single muffler mount bolt under the muffler at the right rear of the bike. Move the pipes forward enough so that there is some clearance when you are ready to remove the head. Then remove the carburetor. I did not remove the screws attaching the adaptor to the head. I simply loosened the screw clamp on the rubber pipe enough that I could move the carburetor to the rear. I suppose that it would have been a little easier if I had removed the air filter box but I am not sure. Once the carb is back far enough that you have some clearance, remove the four large nuts that secure the head. Then remove the two small nuts underneath which take the 10mm wrench. There is one at the rear underneath the carb and one at the very front of the cylinder head. This is a good time in the process to remove the camshaft. Use the procedure in the manual to disable the spring tensioner for the cam chain..it is straight forward. Then remove the bolt from the right side which holds the black plastic chain tensioner guide. Hold onto the guide so that it does not fall into the crankcase. Pull it upward once the bolt is out of position and set it aside with the bolt. Next, use a chisel or screw driver to carefully bend the soft steel keeper washer assembly that secures the two camshaft sprocket bolts to the camshaft. The object is to bend the washer tabs down so that you can remove the bolts. Be really careful here when you remove the bolts because it would be easy to drop the bolts into the crankcase as well as the keeper washer assembly. I suppose you could fish them out with a magnet but it is a lot easier to just not let them fall into the engine! Once you have removed the bolts and the two bolts and the keeper, you will find that the sprocket can be moved to a position where you have enough slack to remove the camshaft...Do not drop the little steel half ring that positions the cam shaft in the bearing bore! Again, it could probably be fished out with a magnet but who wants to take the chance. That being accomplished, you are ready to remove the cylinder head from the cylinder. Grasp the cylinder head with both hands and gently but firmly pull upward. Again, there is room to maneuver the head out under the top frame member but not much..just go carefully and try not to scratch paint on the frame tube. Once you have done whatever you wanted to do to the head..and made any repairs necessary, installation is pretty much the reverse of what you did to get it apart. I strongly recommend the Hylomar jointing compound in the tube as a dressing for the new head gasket and also the gasketless valve cover. Put the black plastic tensioner guide back in, install the bolt and torque it snugly but not too tight.
When you reinstall the camshaft, make sure that you position the T mark in the left engine case hole and line the white mark up at 9:00 o'clock. You push the bike in gear a little bit to get the sprocket bolts in a position where you can get a wrench on them to tighten them up snugly. Make sure to bend the tabs up enough so that they will keep the bolts from coming loose. Make sure that the half ring is back in the groove in the bearing bore. Be careful with torqueing the 6 nuts which secure the head. Make sure you fill the little well under the cams with engine oil...you don't want any dry starts here!! This is an excellent time to take a break..carefully check that everything that you have done is OK. You are about to put the valve cover back on and you want everything to be perfect before proceeding...Once you are sure that everything is positioned OK and that you have properly torqued the six nuts and the sprocket bolts are secure with the tabs. Again check that you filled up the little rectangular oil well underneath the cam shaft lobes! Before you try to install the valve cover, make sure that the two lobes are pointed downwards...rotate the engine by pushing the bike in gear to accomplish this. Then make sure that the parting surfaces on the head and the bottom of the valve cover are clean and dry..no oil here!! Remember, this is a gasketless design so you need to use a sealant here..RTV will work, but you are better off with the Hylomar that you also used on the head gasket or you can use the Suzuki recommended product. Just remember to put on a very thin layer and do not overdo it. Remember to put it on all the parting surfaces..it is important to use it on the parting surfaces that form the camshaft bearing..this is important for preventing loss of oil pressure. Carefully maneuver the valve cover back onto the top of the engine and install the retaining bolts in the correct positions and carefully torque. An additional note here is the installation of the three bolt mount which connects the head to the top frame member; Make sure you get these three bolts as tight as you can without breaking them or stripping the threads...I am not sure of the correct torque but this is important because if they are not tight enough, the vibration will wear marks in the bolts and you may find that there is more noise and vibration when riding than you are accustomed too. If this happens, you will find rust powder around the assembly when you remove the bolts and nuts... Anyway, put the exhaust system back on...you can probably reuse the old gasket washers but it is good to have a couple in stock just in case they leak..they are cheap...put the carb back on, install the tank and make sure to connect both hoses! Do a good final check and you should be good to go...You normally do not have to readjust the valves right away after doing a head gasket replacement but this is based on using a gasket with the same thickness as the old one...Before you put the little valve access covers back on, you can make a quick check. Again, rotate the engine crank in the normal direction of rotation using your finger over the spark plug hole to tell you when the piston is on the compression stroke. The valves are closed when the piston is near top dead center. Reach into the little valve access ports with your fingers and insure that you can feel some some free play. If not, you need to set the clearance before you start the engine..you do not want to risk burning any of the valves. If you do have some play (slack), it is safe to run the engine but it would be a proper procedure to set the clearances with a feeler guage after running a couple of hundred miles....

I hope this helps!

[wdnavion]

I am adding this info to hopefully reduce some confusion regarding the head gasket replacement procedure..

As I stated in the forum, there is not a lot of room between the top member of the frame and the top of the valve cover. If I were going remove the cylinder head again, I would probably use some thin wire ties or possibly some plastic tape to get the wiring harness up on the side of the frame member to get a little more clearance. I think I stated that you want all the valves to be closed when you remove or install the valve cover. This is because the valve springs will push the valve cover up making it difficult to remove and next to impossible to re-install. So the easy way to know that the valves are closed is to remove the spark plug and put the bike in a higher gear and put your finger over the spark plug hole. Slowly push the bike forward until you feel the air pushing out. When you feel the pressure dropping that means that you are at near top dead center and the valves will all be closed. Then you can remove the valve cover. Once you have removed the cover, it is a good time to establish the timing marks so that you will have confidence that you are getting them right when you put the engine back together. Remove the threaded plug in the top of the left hand engine case. Use a flashlight if necessary, but look straight down into the hole as you rotate the engine forward...again you can slowly push the bike forward in 4th or 5th gear until the T mark with the gray paint (in my 2002 bike anyway) is centered in the hole. At that time, if you view the camshaft sprocket from the right hand side, you should have the scribed and white painted mark at precisely the 9:00 position...

Moving on to removing the head, remember that you have to remove the four bolts which mount the exhaust pipe collars. Once you have done that, you will most likely find that you have to remove the single muffler mount bolt under the muffler at the right rear of the bike. Move the pipes forward enough so that there is some clearance when you are ready to remove the head. Then remove the carburetor. I did not remove the screws attaching the adaptor to the head. I simply loosened the screw clamp on the rubber pipe enough that I could move the carburetor to the rear. I suppose that it would have been a little easier if I had removed the air filter box but I am not sure. Once the carb is back far enough that you have some clearance, remove the four large nuts that secure the head. Then remove the two small nuts underneath which take the 10mm wrench. There is one at the rear underneath the carb and one at the very front of the cylinder head. This is a good time in the process to remove the camshaft. Use the procedure in the manual to disable the spring tensioner for the cam chain..it is straight forward. Then remove the bolt from the right side which holds the black plastic chain tensioner guide. Hold onto the guide so that it does not fall into the crankcase. Pull it upward once the bolt is out of position and set it aside with the bolt. Next, use a chisel or screw driver to carefully bend the soft steel keeper washer assembly that secures the two camshaft sprocket bolts to the camshaft. The object is to bend the washer tabs down so that you can remove the bolts. Be really careful here when you remove the bolts because it would be easy to drop the bolts into the crankcase as well as the keeper washer assembly. I suppose you could fish them out with a magnet but it is a lot easier to just not let them fall into the engine! Once you have removed the bolts and the two bolts and the keeper, you will find that the sprocket can be moved to a position where you have enough slack to remove the camshaft...Do not drop the little steel half ring that positions the cam shaft in the bearing bore! Again, it could probably be fished out with a magnet but who wants to take the chance. That being accomplished, you are ready to remove the cylinder head from the cylinder. Grasp the cylinder head with both hands and gently but firmly pull upward. Again, there is room to maneuver the head out under the top frame member but not much..just go carefully and try not to scratch paint on the frame tube. Once you have done whatever you wanted to do to the head..and made any repairs necessary, installation is pretty much the reverse of what you did to get it apart. I strongly recommend the Hylomar jointing compound in the tube as a dressing for the new head gasket and also the gasketless valve cover. Put the black plastic tensioner guide back in, install the bolt and torque it snugly but not too tight.
When you reinstall the camshaft, make sure that you position the T mark in the left engine case hole and line the white mark up at 9:00 o'clock. You push the bike in gear a little bit to get the sprocket bolts in a position where you can get a wrench on them to tighten them up snugly. Make sure to bend the tabs up enough so that they will keep the bolts from coming loose. Make sure that the half ring is back in the groove in the bearing bore. Be careful with torqueing the 6 nuts which secure the head. Make sure you fill the little well under the cams with engine oil...you don't want any dry starts here!! This is an excellent time to take a break..carefully check that everything that you have done is OK. You are about to put the valve cover back on and you want everything to be perfect before proceeding...Once you are sure that everything is positioned OK and that you have properly torqued the six nuts and the sprocket bolts are secure with the tabs. Again check that you filled up the little rectangular oil well underneath the cam shaft lobes! Before you try to install the valve cover, make sure that the two lobes are pointed downwards...rotate the engine by pushing the bike in gear to accomplish this. Then make sure that the parting surfaces on the head and the bottom of the valve cover are clean and dry..no oil here!! Remember, this is a gasketless design so you need to use a sealant here..RTV will work, but you are better off with the Hylomar that you also used on the head gasket or you can use the Suzuki recommended product. Just remember to put on a very thin layer and do not overdo it. Remember to put it on all the parting surfaces..it is important to use it on the parting surfaces that form the camshaft bearing..this is important for preventing loss of oil pressure. Carefully maneuver the valve cover back onto the top of the engine and install the retaining bolts in the correct positions and carefully torque. An additional note here is the installation of the three bolt mount which connects the head to the top frame member; Make sure you get these three bolts as tight as you can without breaking them or stripping the threads...I am not sure of the correct torque but this is important because if they are not tight enough, the vibration will wear marks in the bolts and you may find that there is more noise and vibration when riding than you are accustomed too. If this happens, you will find rust powder around the assembly when you remove the bolts and nuts... Anyway, put the exhaust system back on...you can probably reuse the old gasket washers but it is good to have a couple in stock just in case they leak..they are cheap...put the carb back on, install the tank and make sure to connect both hoses! Do a good final check and you should be good to go...You normally do not have to readjust the valves right away after doing a head gasket replacement but this is based on using a gasket with the same thickness as the old one...Before you put the little valve access covers back on, you can make a quick check. Again, rotate the engine crank in the normal direction of rotation using your finger over the spark plug hole to tell you when the piston is on the compression stroke. The valves are closed when the piston is near top dead center. Reach into the little valve access ports with your fingers and insure that you can feel some some free play. If not, you need to set the clearance before you start the engine..you do not want to risk burning any of the valves. If you do have some play (slack), it is safe to run the engine but it would be a proper procedure to set the clearances with a feeler guage after running a couple of hundred miles....

I hope this helps!

[Water Warrior 2]

Wow, that is a fine write up. Obviously you learned by doing and planning. Let's hope the powers that be make a sticky in the How To's as a permanent record. :2tup: