Convert your GZ250 into a 346cc!!!
 

First off all - I'll give ya a tip - don't ever drill Jets anymore. Many people on this board, including myself tried this at firstm and its just plain dumb.

There are jets for everything , drilling might save you a few bucks, but can cause more damage than help....

The engine in the GZ is from the DR250S (dual-purpose bike). I'm sure there are all kind of stuff that can be found to fit this engine, since it's a smaller version of the DR350 , which had a huge aftermarket possibilities. U don't wanna get to "pipey" cause you want to keep it reliable. I know a Suzuki expert that will definitely have some opinion in that matter. There's many other area's to improve in the chassis, so don't worry about it.

Oh but wait, ... I found one answer here.
Power? More power you say?

Check this out: http://www.thumperracingusa.com/DR250S.html

I am having mine done in a few weeks. Im ordering the parts, and having my own mechanic drop it all in.
Ill have some photos for the process, and I also found a way to extend the fork, found beautiful whitewall tires, found the PERFECT K&N setup, and a way to increase the rear tire size a bit.

These mods, along with a new OEM sprocket, a hotter cam, a z bar, braided hoses, having my engine case dipped in chrome, a chrome battery box mounted, side plate holder, seamless contoured seat, custom grips, fork stabilizer, Euro hand controls, mini tach, tons of white (hidden) LED lights in the frame, custom pipes with mini mufflers wrapped in black, .. man. Its all coming. This is going to be a show bike for sure.

If only I could find someone to help me cut the front fender properly. NATE?!

That would sure make for one heck of a show bike. Sure will be interesting to see this done with the pics and final result. I voted 'go for it', its your bike and if it is what you want, do it!

Looking forward to the pics!

Thanks man.
Yea. Im going for it.

Custom mirrors, lights, foot pegs, headlight, front fender guard from here : http://www.bike-design.com/search.ph...shp_category=0 .. BTW check this out guys.

As well, I want white wall tires, the rear fender cut, and the light relocated to the very back of the seat - bobber style. Chrome stems/caps, and chrome chain.

Man. I just got permission from the wife to take about 3 grand out to play with this bike and trick it out to make it show quality.
I dont know how I did it, but it should be fun. =)

Ill be posting some shots as the project progresses. First is the engine work. =)

My mechanic told me that with what he laid out, and keeping the bike reliable but pushing it to its limmits, it should be pretty damn quick for this type of bike, carb, and little engine. He also tells me that my gas milage will drop a lot .. from about 70mpg to 45, but hey .. its still better than a car. =)

When I first read the topic I thought - Nahhh! But then after reading the post and what you have planned you got my attention. I'll be looking forward to the post/pictures of the progress. Sounds like a fun project.

Cheers!

Parts ordered for big bire kit!

The increase in displacement should make the 250 into a better highway bike with a little taller gearing. Looking forward to the progress reports and pics.

well, its been a month since the last word on this, any info regarding how it went? it looks like a solid mod and i'm considering having it done to my bike if it turns out well.

Workin on it =)

Just waiting for Nate to send the fender back, and a few more mods done to the bike.
I got the parts, and my mechanic installed em. I just have to drop everything back in, and he said something about getting new rings?

Shoud have some pics soon enough.

Sounds like it's going to be a mean machine when you're done with it Jordan! My big thing with the mod (since it's a performance mod) is how the bike performs with the kit. I do a lot of riding back and forth between Tampa and Orlando, and it's rough having semis whip past me at 70-75 to my 60-65. So once you get her up and running, let me know how it rides. If it's a good solid ride, i'm going to get it done ASAP. :D

So how did this mod turn out Jordan? You promised us pictures and feedback, but we still havent heard from you! ;)

Before dropping it in, I need to make sure that everything is for sure.
I dont want my bike destroyed so Im getting a 2nd oppinion, and Ill have photos for you soon. =)

power increase
 

just assuming 13.5 cc's per hp for the GZ. You could expect 7 or 8 more hp. Sounds good. If you do not mind. What did your mechanic charge?

Re: power increase
 

The message you responded to:

Before dropping it in, I need to make sure that everything is for sure.
I dont want my bike destroyed so Im getting a 2nd oppinion, and Ill have photos for you soon.

....was left 5 months ago.

The author seems to have disappeared.
He talked a good story but seldom produced any results.
I can't help but wonder if he ever really had a bike at all.
:roll:

Re: power increase
 

Easy, you got confoozed again. Jordan joined 5 months ago. He posted his most recent thing, the one about making sure that everything is for sure, on july 5th. The date under someone's name (on the left) is their join date. The date at the very top of the post is the day/time it was posted. So in actuality, it was less than a month ago last time he posted.

But jordan, easy has a point, we want results! Some of us would really love a mod like this if it worked!

I can certainly appreciate Jordan's enthusiasm for wanting to make the bike faster. However, if you've read the rest of this topic, it's no secret that I don't think it's possible.

Honestly, for his sake, I hope he hasn't already spent the money on a kit (which he says he already has but no one has seen pictures of it) that can't be used.

He was once a pretty active member who seemed to fall off the horse around the same time that this mod should have been completed.

-Jonathan

Re: power increase
 

:oops: Ya got me! :cry:

Neither the first time nor the last! :roll:

I think he dissapeared. maybe his conversion didn't work out.

Of course it didn't. We tried telling the guy.

I think it would be easier to shoehorn a bigger motor on the GZ250 frame than try to make a big bore kit from scratch, but then unless you got the bike for free or have way too much free time to kill, it would make more sense to just buy a bigger bike. Maybe Jordan figured this out.

As was mentioned before, $500-$1000 for 3-8 HP isn't really worth it.

Re: Convert your GZ250 into a 346cc!!!
 

Without even looking I can say: Go for it and let us know how it turns out! :whistle:
We will be forever greatful. :biggrin:

PS I like your tag line. :2tup:

Re: Convert your GZ250 into a 346cc!!!
 

Keep an eye out for LS650/S40 too. Some of the older models have buckhorn bars; had I known that, I might not have the GZ. Now that I do, I probably won't change but I think that "CC envy" is a chronic disease that one never quite gets over completely. :cool:

Re: Convert your GZ250 into a 346cc!!!
 

Don't know. I have been avoiding looking at them TOO closely for fear that I might decide I HAVE to have one! :roll:

Re: Convert your GZ250 into a 346cc!!!
 

I think it existed, it is just that he didn't ever actually do all this stuff he claimed he was gonna do to his bike and he didn't want to come on here and have to admit that he was full of S#@t. But he has been back a couple of times since, he just has commented on this thread, he also claims that he now rides a Ducati, as if that is supposed to mean something to us.

Re: Convert your GZ250 into a 346cc!!!
 

In addition to those parts you may well have to use a different/larger carb. More $$. Maybe a custom exhaust pipe and aftermarket fit-all air filter. Might be more advantageous to look for a nice used S-40 for the extra grunt and only weighs 60 lbs more. A bit larger than the GZ overall with only a couple factory gremlins. One being a lean carb mixture(easily fixed) and the other being a valve train piece that is replaceable with better aftermarket product if needed. The bike as a whole is really just a big GZ with a belt drive IMHO.

Re: Convert your GZ250 into a 346cc!!!
 

motorhedfred,
first off I'm not trying to discourage you. I'd love to have a 300 or 350 to ride. I think it would take some serious machining and custom work to shoehorn a 350 piston on the GZ250 engine. Even supposing that you could simply replace the top half on the engine with that of a DR350 there is the problem that the DR350 engine has a 10mm longer stroke. 71.2mm vs 61.2mm. You would have to shorten the barrel by 10mm yielding you a 300cc engine. Comparing the bore of the DR350 to GZ250, 79mm vs 72mm. I think the best probability for an improvement would be if there's enuff meat in the GZ250 barrel to do a resleeve to a 79mm bore Which would yield a 300cc engine. An awful lot of work for maybe an extra 3-5 HP. I'm keeping an eye out for a DR350 engine to see if I can shoehorn it on the GZ250.

Re: Convert your GZ250 into a 346cc!!!
 

If there is any practical way to increase the displacement, I think that is probably the only way.

After you do ALL the other checks on the piston, etc. then there is the SHAPE of the piston dome for valve clearance. Those spec's are often VERY hard to find.

Re: Convert your GZ250 into a 346cc!!!
 

Was just doing some thinking about what would be necessary to convert the GZ250 to a 350 Using DR350 parts. This is of course assuming the parts would physically fit. You would definitely need the following from the DR350 engine:
Piston
Cylinder sleeve
Crank shaft
you might need the following from the 350 engine:
cam chain
cylinder head.
The way I would envision this is that you'd have to swap the crank shaft to add the extra 10mm stroke. the 350 sleeve would be necessary to accommodate the increased stroke and then obviously you'd need the 350's piston. I'll assume the connecting rods are the same. I would think you should be able to use the 250's cylinder head. This would make it easier to not have to do any custom exhaust work and worry about the carb fitting. I also would think the cam chain could be reused from the 250, but you may have to use the 350's cam chain if the 250's chain doesn't fit due to increased stroke distance.

This would seem to be cost prohibitive and time consuming. A more economical approach would only get you a 300cc engine but would have more likelihood of success. This would be to have a machine shop bore and resleeve the GZ250's cylinder jug to accommodate the DR350's piston. The only problem would be whether or not there is enough material in the GZ250's cylinder jug to fit the larger piston sleeve.

I hope this give you some food for thought. Motorhedfred, I see you're in Ohio too. Depending on how far away you are if you do decide to attempt this, I'd be willing to offer a hand.

Give these guys a call maybe they could come up with something.
http://kustom-kraft.com/SUZUKIKITS.html

Re: Convert your GZ250 into a 346cc!!!
 

There are clearly forms of entertainment that I will never understand. Doesn't Suzi already make a bike that's about the same size as the GZ but with a bigger engine? Also, I think I could appreciate the thinking behind a retrofit that took it from 250 to say 500 or 600 but to 350 seems pretty unimpressive. Still, I will probably be just as curious as everyone else if you actually make it work, or even if you escape without embedding piston or cylinder shrapnel in your behind.

Re: Convert your GZ250 into a 346cc!!!
 

I think so but not available in North America. Next one here is the S40/LS650.
Some days, I wish I had one; most days not.

Re: Convert your GZ250 into a 346cc!!!
 

Another Problem with the Boring out the GZ's cylinder to make it a 300cc is the same problem you have on a car engine only its gonna be magnified on The GZ because it is strictly air cooled, It is probably gonna overheat like hell every time you ride it.

I had a Chevy truck with a little straight six in it that I decided to be different and bore out and put a different cam in and all that, because I had never seen one done that way, it ran hot every time I drove it, and I couldnt take back what I did to it without alot more expense, so I ended up junking the engine.

Re: Convert your GZ250 into a 346cc!!!
 

If you machined the case to accept the 350cc cylinder, then the new cylinder should be finned correctly for the displacement. I would be surprised if the GeeZer cylinder has enough meat to take it out a 350cc.

IMHO, I think y'all are jerkin off. Just buy a bigger bike. Find a nice older 350 and put some $$ into it. A nice Honda 350 Four.............

:jo: :jo: :jo: :jo:

Re: Convert your GZ250 into a 346cc!!!
 

When you find one Sarris you let me know :rawk:

Re: Convert your GZ250 into a 346cc!!!
 

.....I honestly can't believe that this is still being discussed.

Re: Convert your GZ250 into a 346cc!!!
 

I know! I mean, I just can't understand why someone would be talking about trying to make something that falls in between a 250 and a 600+ since there is NOTHING that exists in the category. I mean come on people! strap on a pair and go get a 600lb+ 650cc already! :neener:

Who knows maybe somebody will come up with something that is cost effective. I doubt it though. Although "cost effective" is in the eye of the beholder.

Re: Convert your GZ250 into a 346cc!!!
 

V-Star 650 Classic. Definately a nifty bike.

:)

Re: Convert your GZ250 into a 346cc!!!
 

There are plenty of 500s....

If you were the one looking for a drop-in motor, try ROTAX.

Re: Convert your GZ250 into a 346cc!!!
 

There are only plenty of 500's if you want to go from a cruiser to a sport bike, as far as I know Kawasaki is the only one who still makes a 500 cruiser.

Re: Convert your GZ250 into a 346cc!!!
 

I with ya on this. My wheel chair may have a smallblock Chevy. A good friend of mine
built a 426 Hemi into an original Minicooper. Why? Because he could!
:2tup: :2tup: :2tup:

Re: Convert your GZ250 into a 346cc!!!
 

I see no reason to contribute to this thread because:

The original "kit" that was supposed to be a drop-in for the GZ250 would not fit. The "kit" itself did exist and it still does. As mentioned, it is a big bore kit for the Suzuki Dr250. While similar, these engines are not the same. As a result, the thread was dropped and, I thought, it was dead. Jordan came in here with all kinds of claims of modifications that he was going to do, or that he had done, but never gave a single shred of evidence, except for claiming that he could smoke anyone in city traffic and that his "mechanics" had done more work to this bike than any other GZ EVER!!!!!! YEAH!!! The majority of his posts, as substantiated by just reading over them, made very little contribution to the knowledge base of this forum and were almost purely far-out speculation. (Like this BIG BORE kit)

Secondly, unless you have lots of spare motors lying around, which you can butcher to get parts, and have all of the tools necessary for the endless amount of work that you will have to do to gain these "precious" few horsepower and come away with a reliable engine, even then, even after all of that work, money and time, you'll essentially just be left with a slightly faster version of the same exact bike as everyone else.

I can appreciate your obvious knowledge of engine internals and the corresponding math, but this is something that just won't ever be worth the trouble. What we're essentially talking about is, I'd say, a minimum of $1000 (I'd expect much more) for a few MPH on the top end and some more low-end grunt. For the same amount of money, or time, you can get a much more reliable bike, which will outperform anything that you can build (no offense) for less than $1000 more than the cost of a GZ.

Can you build anything you want? Of course you can.
Will it later only be worth a fraction of the time, and money, and sweat that you put into it? Of course it will.
Will it ever be as reliable or as economical as just buying a bigger bike? Of course not.
Will having a highly modified GZ250 be a neat novelty that is worth a look or two before it fades away as an afterthought? Of course it will.