300cc tuning and performance - Page 4

Water Warrior 2 · 01-27-2018, 02:26 PM

Oh my, you are really getting down to the Nitty Gritty with everything. 30 rear wheel horsepower would be awesome on a GZ. You would be able to frighten a lot of bigger bikes due to the power to weight ratio.

A GZ with a blower! It must have had a bucket full of mods to even run properly. Sounds like a short life engine if opened up on a regular basis. But what the h**l, it was likely a different way to get where you want to be with the GZ without a large cost.
I find these projects very fascinating. They are works of art in some cases and deserve to be appreciated for their effort and planning.

kilo0195 · 01-29-2018, 02:54 PM

https://ibb.co/kKd9KR

My "shadow" couldn't wait to get out on the bike especially as he said I had to "prove to him" it was going to be faster lol.

Water Warrior 2 · 02-07-2018, 11:35 PM

Quote:

Originally Posted by kilo0195

https://ibb.co/kKd9KR

My "shadow" couldn't wait to get out on the bike especially as he said I had to "prove to him" it was going to be faster lol.

Another generation of riders. Take care with him and always answer his questions. Your answers will determine his future decisions in life.

kilo0195 · 02-14-2018, 09:22 PM

So the bike has been neglected for a couple weeks as I've been busy working. Figured I'd try and get the carb sorted and still not done with that. Put the stock 52.5 starter jet in, swapped the 17.5 pilot with a 20, and changed my 147.5 main to a 150... Kept needle the same. Seems good until around 2/3 to 3/4 throttle. Full throttle she stops cutting out but still underpowered. Going to try and change my needle with one that has more taper. I can't shim the thing anymore. I actually had to cut about 1/8" off the top of the needle already to get it to fit with the shim it has lol. If the taper doesn't do it then I'll try a 152.5 main. Plug was light grey driving around with big under 1/2 throttle so I'm confident I'm good on the pilot at least. I really would love to have one of those ecotron efi deals.

kilo0195 · 02-18-2018, 03:17 PM

Anyone still curious I've got the carb dialed in finally. 22.5 pilot with 1.5 turn out on mix screw. 52.5 stock starter jet, and 150 main jet. The needle was the fun part. I boought another stock needle for security then took my original to the wire wheel on my bench grinder. Slowly removing material and increasing the taper. This took some patience and nerve (The last part being why I bought another stock needle). I'm glad I went this route because with as much as I took off I'd have spent a fortune in different size needles finally getting to where I was. The bike is finally running where it should and has a nice smooth transition between all throttle ranges. I'm sure it's not perfect and will still need dyno tuned, but at least I'm not frying a piston or looking like I'm rolling coal in a diesel lol.

kilo0195 · 03-08-2018, 01:33 PM

Another note of interest... you can use the stock 250cc head gasket with the 300 as long as you have the piston clearance. The gasket I used after the last mods failed which left me with only the stock gz gaskets or a custom copper one. The stock gasket doesn't have a fire ring so I figured I'd give it a shot. I put the jug on and spun the piston to TDC and I had about .012 sticking above the deck. As this would mean the piston would be striking the head gasket I decided to add another .033 thick paper gasket between the jug and crankcase. This in essence raised the jug enough to give me the deck clearance for the stock gasket. This should bump CR to almost 11/1 now. It's running great for now. My only concern is the gasket material that is now in the combustion chamber. I don't imagine it breaking up as it's stacked steel. I could though foresee it causing detonation if the steel gets hot enough and can't dissipate that heat. So far so good, yet its still cool temps here. I will update if anything changes. PS I'm still slightly pissed about the gasket failing in less than 1000 miles.

kilo0195 · 04-23-2018, 07:25 PM

Everything is still running well. I've been playing with the cam timing a lot. Right now I'm at 6° advance and might keep it there. Definitely has a little more balls around town and slower speeds on the highway. The needle only goes to 88mph so shifting the power band up another thousand rpm doesn't do much good... especially as the goal was to keep it reliable. Downside is the advance means more heat, which is rather noticeable, so the oil cooler is a must before summer temps hit. I also replaced the rear shocks again, this time with a combined spring weight of 1400 pounds. This stiffens the rear up some, but makes it able to actually ride 2up without bottoming on bumps. Think I'll probably end up keeping this one as shes pretty dependable, and light enough I can throw it on the hitch carrier when we go on trips. It's nice being able to take a bike with us when we go to the mountains.

kilo0195 · 04-26-2018, 10:26 AM

Well she does better than I thought. I had someone get on the back with me... they weigh about 230# and I weigh about 160#. So we had around 390# of rider on the bike. The shocks kept it from bottoming and also still maintain a smooth ride. The real shock was I was able to maintain 65mph. Granted she had no torque left, but I'm also running a 16t front and 39t rear sprocket. If I were to switch the front or rear back to the stock 15t or 41t then I imagine she wouldn't be maxed at 65mph. Now the only time I'd ride 2up with that much weight would be around town maybe, but still is nice to know that she has the ability now to do this.

kilo0195 · 04-27-2018, 07:08 PM

So aparently I spoke too soon. Was riding today when all of a sudden the bike just stopped while I was idling at a light. Motor wouldn't budge. Fearing I dropped a valve I pushed it back and tore it apart. What I found was that an intake valve guide had broken apart at the bottom and fell into the cylinder. Thankfully the walls look fine, just the piston top and head have a nice little dimple which should be fixable. I'll inspect the rod, pin, etc later to make sure the sudden stop didn't crack anything. The valve itself looks ok... won't know for sure till I take them out. I've never had a valve guide catastophically fail like that before. Good news is motor is ok... bad news is I'm not sure what caused the failure. If it was exhaust I'd say excessive heat, but it's the intake side.

kilo0195 · 04-28-2018, 08:02 PM

Upon close inspection I found the culprit. The cam was advanced too far for the build and at high rpm was allowing the intake valve to contact the piston crown. I found some slight scuffing in the valve reliefs on the crown. The repeated contact would have caused enough shock over time to crack the guide. Valve is still straight somehow and retainer looks fine as well. Bad news is I think the piston has a hairline crack at the base of the pin... and the top ring journal is compacted down pinching the top ring on one side. Looks like I'll be needing a new piston. So the moral of the story kids is dont deck it too much or advance the cam too far. Found another 78mm piston on Ebay and will be ordering that along with some new guides and all should be good.

01-27-2018, 02:26 PM	#31
Water Warrior 2 Senior Member Join Date: Dec 2006 Location: Squamish B.C Canada Posts: 11,409	Oh my, you are really getting down to the Nitty Gritty with everything. 30 rear wheel horsepower would be awesome on a GZ. You would be able to frighten a lot of bigger bikes due to the power to weight ratio. A GZ with a blower! It must have had a bucket full of mods to even run properly. Sounds like a short life engine if opened up on a regular basis. But what the h**l, it was likely a different way to get where you want to be with the GZ without a large cost. I find these projects very fascinating. They are works of art in some cases and deserve to be appreciated for their effort and planning. Login or Register to Remove Ads
	2

02-18-2018, 03:17 PM	#35
kilo0195 Member Join Date: Jul 2017 Location: Illinois Posts: 52	Anyone still curious I've got the carb dialed in finally. 22.5 pilot with 1.5 turn out on mix screw. 52.5 stock starter jet, and 150 main jet. The needle was the fun part. I boought another stock needle for security then took my original to the wire wheel on my bench grinder. Slowly removing material and increasing the taper. This took some patience and nerve (The last part being why I bought another stock needle). I'm glad I went this route because with as much as I took off I'd have spent a fortune in different size needles finally getting to where I was. The bike is finally running where it should and has a nice smooth transition between all throttle ranges. I'm sure it's not perfect and will still need dyno tuned, but at least I'm not frying a piston or looking like I'm rolling coal in a diesel lol. Login or Register to Remove Ads
	3

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01-29-2018, 02:54 PM	#32
kilo0195 Member Join Date: Jul 2017 Location: Illinois Posts: 52	https://ibb.co/kKd9KR My "shadow" couldn't wait to get out on the bike especially as he said I had to "prove to him" it was going to be faster lol.
	0

02-14-2018, 09:22 PM	#34
kilo0195 Member Join Date: Jul 2017 Location: Illinois Posts: 52	So the bike has been neglected for a couple weeks as I've been busy working. Figured I'd try and get the carb sorted and still not done with that. Put the stock 52.5 starter jet in, swapped the 17.5 pilot with a 20, and changed my 147.5 main to a 150... Kept needle the same. Seems good until around 2/3 to 3/4 throttle. Full throttle she stops cutting out but still underpowered. Going to try and change my needle with one that has more taper. I can't shim the thing anymore. I actually had to cut about 1/8" off the top of the needle already to get it to fit with the shim it has lol. If the taper doesn't do it then I'll try a 152.5 main. Plug was light grey driving around with big under 1/2 throttle so I'm confident I'm good on the pilot at least. I really would love to have one of those ecotron efi deals.
	1

03-08-2018, 01:33 PM	#36
kilo0195 Member Join Date: Jul 2017 Location: Illinois Posts: 52	Another note of interest... you can use the stock 250cc head gasket with the 300 as long as you have the piston clearance. The gasket I used after the last mods failed which left me with only the stock gz gaskets or a custom copper one. The stock gasket doesn't have a fire ring so I figured I'd give it a shot. I put the jug on and spun the piston to TDC and I had about .012 sticking above the deck. As this would mean the piston would be striking the head gasket I decided to add another .033 thick paper gasket between the jug and crankcase. This in essence raised the jug enough to give me the deck clearance for the stock gasket. This should bump CR to almost 11/1 now. It's running great for now. My only concern is the gasket material that is now in the combustion chamber. I don't imagine it breaking up as it's stacked steel. I could though foresee it causing detonation if the steel gets hot enough and can't dissipate that heat. So far so good, yet its still cool temps here. I will update if anything changes. PS I'm still slightly pissed about the gasket failing in less than 1000 miles.
	2

04-23-2018, 07:25 PM	#37
kilo0195 Member Join Date: Jul 2017 Location: Illinois Posts: 52	Everything is still running well. I've been playing with the cam timing a lot. Right now I'm at 6° advance and might keep it there. Definitely has a little more balls around town and slower speeds on the highway. The needle only goes to 88mph so shifting the power band up another thousand rpm doesn't do much good... especially as the goal was to keep it reliable. Downside is the advance means more heat, which is rather noticeable, so the oil cooler is a must before summer temps hit. I also replaced the rear shocks again, this time with a combined spring weight of 1400 pounds. This stiffens the rear up some, but makes it able to actually ride 2up without bottoming on bumps. Think I'll probably end up keeping this one as shes pretty dependable, and light enough I can throw it on the hitch carrier when we go on trips. It's nice being able to take a bike with us when we go to the mountains.
	1

04-26-2018, 10:26 AM	#38
kilo0195 Member Join Date: Jul 2017 Location: Illinois Posts: 52	Well she does better than I thought. I had someone get on the back with me... they weigh about 230# and I weigh about 160#. So we had around 390# of rider on the bike. The shocks kept it from bottoming and also still maintain a smooth ride. The real shock was I was able to maintain 65mph. Granted she had no torque left, but I'm also running a 16t front and 39t rear sprocket. If I were to switch the front or rear back to the stock 15t or 41t then I imagine she wouldn't be maxed at 65mph. Now the only time I'd ride 2up with that much weight would be around town maybe, but still is nice to know that she has the ability now to do this.
	0

04-27-2018, 07:08 PM	#39
kilo0195 Member Join Date: Jul 2017 Location: Illinois Posts: 52	So aparently I spoke too soon. Was riding today when all of a sudden the bike just stopped while I was idling at a light. Motor wouldn't budge. Fearing I dropped a valve I pushed it back and tore it apart. What I found was that an intake valve guide had broken apart at the bottom and fell into the cylinder. Thankfully the walls look fine, just the piston top and head have a nice little dimple which should be fixable. I'll inspect the rod, pin, etc later to make sure the sudden stop didn't crack anything. The valve itself looks ok... won't know for sure till I take them out. I've never had a valve guide catastophically fail like that before. Good news is motor is ok... bad news is I'm not sure what caused the failure. If it was exhaust I'd say excessive heat, but it's the intake side.
	0

04-28-2018, 08:02 PM	#40
kilo0195 Member Join Date: Jul 2017 Location: Illinois Posts: 52	Upon close inspection I found the culprit. The cam was advanced too far for the build and at high rpm was allowing the intake valve to contact the piston crown. I found some slight scuffing in the valve reliefs on the crown. The repeated contact would have caused enough shock over time to crack the guide. Valve is still straight somehow and retainer looks fine as well. Bad news is I think the piston has a hairline crack at the base of the pin... and the top ring journal is compacted down pinching the top ring on one side. Looks like I'll be needing a new piston. So the moral of the story kids is dont deck it too much or advance the cam too far. Found another 78mm piston on Ebay and will be ordering that along with some new guides and all should be good.
	1