Counterbalanced Engine

[farmerj]

Hi all,

I've been researching the possibilities for a Counterbalanced engine, and thought I'd post what I've found for others who might be interested. I must say I've never ridden one, but I'm interested in an engine that's smooth and more "trials-like" down low, and this seems like a fun project.

The bottom line as I see it, is that if you want a CB'ed 300cc engine get a '96-'98 engine and machine the cases to accept a 300 cylinder, or get an engine from a 300 Wild quad.

Thanks goes to Jim Cook for sharing his expertise and knowledge.

Feel free to contibute yours as well!

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Originally Posted by farmerj
Hi Jim,

Don't know if you have time for questions!

I'd love to try a counterbalanced engine...Is it worth messing with?

Are there any used counterbalanced engines out there? Is it cheaper just to buy the whole bike?

I loved the Smackover website. Wish I had the "counterbalanced" threads from there! I remember one discussion about a company in California that would machine/match the cases & balance the crankshaft (?) and smooth out the newer engines.

Does that "ring a bell" to you? Does it work?

You are revered in GasGas land!

Thanks,

Jeff


Although the counterbalancer can be relatively easily added (with some machine work) to the '99-'00 engines), it's better to just get a '96-'98 (and early '99 model engines, which were actually left over '98 engines) and install one in a newer frame. (I'd suggest a '2005 or 2006 frame.)

To make the older counterbalanced engine fit into the newer frame, you will only need to have the water inlet on the head machined down to increase the clearance between head/water inlet and the fuel tank. (If you compare the height of the water inlet on the head of the new engines with the water inlet on the '98 engine's you will quickly see what I'm talking about. Everything else should fit just fine.

The true '99 engine is when the changes to the cylinder and head were put into production, and the counterbalancer was removed. The new cylinder and head can be used on the older cases, but some machine work would be necessary to fit the newer cylinder's skirt down into the older cases.

The '99 & '00 engines will take the counterbalancer, but will take a line sight boring job to get the bearing/seal faces true to the CB shaft.

The '01 year was when the changes to the crankshaft and crankshaft bearings were implemented. Some internal castings changes made the counterbalancer no longer an option to this engine.

'05 was when the cases were changed completely in the ignition area (where the counterbalancer rotated).

I think that Steve Marolda at Moto West was doing the engine balancing that you speak of. He does excellent work, but it really isn't needed (in terms of smoothness), with the counterbalancer installed.

Thanks for the kind words. Don't hesitate to contact me for any help I might be able to give. Feel free to share this information with anyone who might benefit from it.

Take care,
Jim

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Originally Posted by farmerj
Jim,

That information is so helpful! It clarifies some mis-information I've seen out there. I may compile some of this and make a post on the forum for others who are interested in the CB engine.

You kind of "opened the floodgate" with your openness to help. Don't feel obligated to respond to all of these questions...

1. My understanding is that the all of the '96-'98 CB engines are 250s - no 300s made until '99. Is this true?

2. Have you ever heard of or ridden a CB'ed 300?

3. If a guy wanted a CB'ed 300, it looks like the options are:
a) Machine the cylinder skirt from a newer 300 engine and fit it to the '96-'98 cases.
b) Add a CB to a '99-'00 300 engine (with some machine work.)
c) Use an engine from a "Wild" 300 quad, as they are counterbalanced. Would this work? Is the ignition different than on the enduros?

Which is the best route?

4. Jim, at one point you said:

I absolutely love my 2006 300. It's the best bike that I've ever owned.

So is my desire to run a CB motor misplaced?

Thanks so much!

Jeff


Hi Jeff,

I'll address your questions by the number.

1.Correct. I know of a few '99 300 cylinders that were installed on the earlier cases to make counterbalanced 300s. That is where I learned that the cases need to be cut a bit to allow the larger skirts of the '99 cylinder to be used. (the skirt is larger in the '99 and later engines, which also have a slightly larger "water jacket".)

2. I have not ridden a c/b 300. However, I did have a '98 250 cylinder bored to fit a
Wiseco 14th oversize TRX250R piston (and then recoated with nikasil and honed to a precision fit) to make it a 274cc. I ran this engine for four more years. (I also had to shave the powervalve flapper for clearance.)

3.
a. No. Machine the hole in the cases to allow the '99 300cc cylinder skirt to enter.
b. Yes, but the work consists of a "line sight bore" of the place where the counterbalancer shaft, bearings, and seal will run and seat. It looks more simple than it is. (It looks like one would just have to drill a hole for the shaft, but this didn't result in the bearings being properly aligned; so a "case split line sight bore" from a machine shop is required for a good job.
c. It would work perfectly. If you didn't like the ignition, you can just swap with one off a bike. The basic part of the ignition is the same (it uses the smaller XC ignition with the 35w lighting coil, and also has the original '98- GasGas EC setup with the magnesium ignition cover with the Ducati style add-on extra 100w lighting setup. The extra lighting windings are bolted to the inside of the ignition cover and the rotating magnets are carried by a piece that is essentially an external flywheel weight on the outside of the flywheel), but the cdi is different for the quad engine. (As I said, the quad engine uses the same original ignition and lighting set-up as the '96-'98 EC engines (which first saw production in the '97 model bikes).

If you want a counterbalanced engine in your bike, then either use a quad engine, or install the older engine in a '05 or '06 chassis (or later)... (I'm not as familiar with the newer chassis, but love the geometry of '05 & '06 bikes.) The quad will be a 300 and, with no modifications, the older EC engines will be a 250cc. There is really no other difference.

4. Not at all. I just love my '06 300. But...I still want one with the counterbalanced engine, too...

Good Riding!
Jim

 

[farmerj]

Second post on the CB'ed engine

Here's another post from Jim, with more info. Thought I'd make a second post so that the first one wasn't sooo long.

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http://www.gasgasrider.org/forum/showthread.phpt=9097&highlight=counterbalancer&page=2

From Neil E...

For those wondering about counterbalanced GasGas engines, here is what Jim Cook sent to me when I asked his opinion on a potential project.

The following is the best of my knowledge, from speaking with former GasGas tech help people, and from speaking with dealers who tried different experiments. The last set of bike cases which easily take the counterbalancer shaft are the "true" '99 model bikes. In 2000, or 2001, the cases were slightly modified for strength, which put some of the castings in the way of a simple "line sight bore" to get the shaft and bearings in proper alignment.

In the "true" '99 engine, the opening in the cases is large enough to accept the 300cc cylinder without modification. I think that the holes for the c/b shaft will have to be bored in that model cases. It's either that, or if the holes are there, one needs to have the cases machined (line sight bored) to to make sure the holes and bearings are properly aligned.

In the '96 model through the '99 Prototype (early model) 250s, all were predrilled to accept the c/b shaft, with the motocrossers (without the c/b shaft) having a metal plug inserted in the ignition side to keep the oil from getting through to the ignition. These cases will have to be slightly trimmed to accept your slightly larger 300cc cylinder skirt.

The 300cc quad engine is essentially a "true" '99 300cc engine, with the cases bored to accept the c/b shaft. It even has the larger magnesium ignition cover that the '96-'98 came with (to allow the extra lighting capacity). If you go this way, get an early model 300cc quad engine, without the reverse.

In 2005, they changed the cases so that the hump in the cases where the counterbalancer weight spun is no longer full size, but only large enough to allow the pick-up coil to be installed there when the larger EC ignition is used.

Even though the 2000 through 2004 cases have the full sized round "hump", the cases are not conducive for installing the countebalancer easily.

With the counterbalancer installed, one will need to run the smaller flywheel mx ignition, because of the need to mount the pick-up coil at the "8 o'clock position, since the counterbalancer weight is taking up the space in the hump. (If you desire more lighting capacity, the magnesium ignition cover will allow you to run the original Ducatti style lighting system.)

I believe all of these engines will mount in any of the 200cc to 300cc bike frames, of any year. One thing, though: The water intake casting on the '96-'98 engines is very tall, and will have to be machined down lower to match the height of the '99 and later engines, in order for there to be enough room for it to fit under the fuel tank.

Also, the counterbalancer shaft will act a bit like an extra flywheel weight. Not a big difference, but it will make a difference.

I hope that this helped you. If you do install the counterbalancer, you will be amazed at how much smoother the engine runs, especially at higher rpms. I really liked it, and rode my '99 prototype (which came with a '98 engine) as my primary bike for almost six years.

I don't have any experience with 2007 or later bikes, but definitely prefer the 2005 and later chassis to the earlier models, except for the 1998 chassis. I really like the 1998 chassis with the 2004 and later Marrazocchi 45mm or 50mm Shiver forks. (The 1998 chassis was different from the earler models, and turned much better and was more stable than the '99-'01, and turned better than the 2002-2004 chassis.

I really liked the changes that were made to the 2005 chassis, and the look of the black powercoated but otherwise identical 2006 chassis. I absolutely love my 2006 300. It's the best bike that I've ever owned.

 

[farmerj]

Quad engine question...

FYI, a comment on the quad engine from another forum member:

The 300 did not come out till 99 on the non CB engine and the 300 cyl will not fit into the 97-98 cases from what I'm told.The wild 300 had a CB but had a high failure rate of the CB shaft, why I'm not sure but many wild owners took the cb shaft out and put auto freezer plugs in.
Steve (Cruiser)

Here's a post that refers to the same issue:

http://www.gasgasrider.org/forum/showthread.php?t=8022

I don't know if the quad CB setup is different from the enduro motor, or if quads are just ridden in a way that contributes to a CB shaft problem (hi-rpms?) I haven't heard of complaints regarding CB shaft failure rate in the motorcycles? Any comments out there about quad engine CB reliability?

Jeff

 

[farmerj]

CB ride reports

Lastly (at least for now), a few ride reports. Feel free to add yours!

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...a comment from another post:

To absolutely get rid of vibration related problems, I suggest a GasGas EC; with a '96-'98 engine installed. Those engines have a gear driven counterbalancer installed, which eliminate vibration. They are amazing, and will fit into any '96-'09 GasGas EC/XC/DE chassis.
Good Riding and Best Regards!
Jim Cook


...a ride report from "Cruiser":

The CB engine is a very different beast compared to the newer bikes. I've ridden GMP's 07, his 03 and 01 and I had a 03 like his but set up very different. Mine revved up a tad slower if you were in sand but getting into a mud hole or a rocky climb it felt more like a trials bike.. couldn't slow the thing down.. very 4 stroke/tractor like in that regard. You could get the rpm's to pop like a trials bike at low rpm but the engine has momentum if you know what I mean.. its fun and different.. One the pipe it really opens up and the effects of the CB go away.. and that is why Jim Cook of the original gg board (smackover) would refer to his 98/99 cb bike the 3-stroke- his little spanish dancing girl.
Steve

 

[Cruiser]

My 97 250 was a better powerhouse than my 03 250.. GMP's 03 was faster than my 03 but he set his up completely different and spent lots of time doing so.. Had the V-force reeds before anybody else.. I went more linear with my 03 but I never got the feel the 97 had.. the limiting factor on my 97 was the suspension.. the geometry of the frame is good but the 45 conventional zokes were not.. I was real close to swapping in my 97 engine into my 03.. never did it.. but it did cross my mind.. My 97 runs a honda cr piston, and the different skirt gave it a better low end response, the reeds were CF from Steve at Motowest and I have currently a fmf pipe and procircuit isde s/a from a ktm on it. Best power came from the motowest prototype pipe the bike came with when I got it.. and the stock silencer with no s/a.. this was also very quiet.. The messico I have is great power but a soft pipe. I have run this bike in the stock 13/46 gearing and it worked,, never needed more than 13/50.. My 03 I ran a 13/52. The 97 pulled harder on the hills. Climbs were easier.. I almost should not sell her..

 

[GMP]

I don't think a pre '05 motor will go into a '05+ frame, lower motor mount is different, and pre '03 motors had smaller dia swing arm pivot bores.

 

[firffighter]

Jeff,

Great topic and interesting thoughts. After riding my 300 you get an idea on how much vibration a 300cc 2-stoke has. Just for your info, my Gasgas is much quieter in terms of vibration than my KTM300 by a long shot. Try a YZ250 and you get a whole new appreciation for the Gasgas's lack of vibration.

I would love to try a CB engine and I think the reports of trials like power delivery sounds awesome.

One thing to consider is that you can get the zoke conventionals to perform very well. I had a '98 KTM200 with zoke conventionals reworked by House of Horsepower that were the best performing woods forks I have ever had! Dwight Rudder over on Thumper Talk has some strong thoughts on conventionals and his opinion is that with proper setup they can out perform USD forks in the woods, hands down. IMO, properly setup conventionals are sweet forks for the woods. USD's work well for higher speeds, whoops, catching sweet air, etc., but I really like conventionals for the Northwest woods riding we like.

So, if you could get a great buy on a CB bike, and rework the suspension, I think you would have a pretty sweet woods bike. You could send those forks off to WER who is the leader in reworking conventionals, add one of their dampers and have a pretty sweet setup.

The only issue that you might have in owning an older Gasgas is getting parts, but I have not done any research into that issue. I would think a note to Gofaster might answer that one.

 

[Cruiser]

As for parts,, not many parts that dont cross over except for fuel tank, seat and rad shrouds,, The 97/98 had a projection on the cyl head that would interfere with the 99-later fuel tank(where the lower rad hose "T" fitting bolted on) and you could not mount the more readily available 99- newer tank/seat and shrouds.. in many colors..I had my cyl head machined down and should clear the tank no issue. Have not tried it as of yet due to the simple fact that I dont have one to try on.. If I had a smaller newer style ign coil the T fitting could be reversed 180 and more clearance would be gained.. The 97 has a big honking coil.. and its inside near the head.. As far as the forks, I did get my forks working well.. but they lacked a lot compared to worked USD forks.. I talked to Drew at WER in detail and modified the internals to get them better.. and they work great going fast in the rocks.. issue is they can be made to work one place well.. not many places.. and the fork seals are getting hard to find on the 45 conventionals.. which you need to swap out or clean out every other ride.. Seeping is a "normal" condition on the zoke 45's.. You can also feel the flex.. rear is great!

 

[GMP]

Zoke 45 Magnums are not hard anodized internally, so they are in self destruct mode from the start. Thats why the oil always looks like silver/grey paint when you change it. Crude fork. The conventionals that work real well well are the Showas from an old RMX or RM 125. I have a friend that puts a set of these on every new KTM he buys.

 

[Neil E.]

I don't think a pre '05 motor will go into a '05+ frame, lower motor mount is different, and pre '03 motors had smaller dia swing arm pivot bores.

I would think the frame mounts could be cut off and rewelded to suit an old motor. Is there enough meat on the cases to open up the swingarm pivot bore?

 

[GMP]

Anything is possible with a little time and/or $$. I was talking about a simple R&R.

 

[firffighter]

Well, to each his own, but the 45 Zokes on my '98 KTM200 exc were great in the rocks, roots and logs here in the tight Oregon trails. The fork flex that many complain about can be an advantage in the slow nasties. I am not sure if House of Horsepower is open for business anymore, but they really had my Zokes dialed in and they were magic in the woods.

I also owned a KTM300 with WP 50mm conventionals. They were also nice tight woods forks with less flex than the 45's. I still liked the 45's better, but I think it was because they were set up specifically for my liking, whereas the WP's were set up by previous owner who did a bit of MX.

If I were doing more high speed riding or thought about doing some racing, then I think the forks would be a bigger issue. But, for trail riding, they are darn good. Heck, even those miserable KDX forks can work well in the woods

 

[Cruiser]

The ktm zokes and the GG zokes were very different forks,, in fact,, I have 97 KTM lowers on my GG 45's now as the GG lowers were junk,, would muddy the oil as soon as you used them.. Issue is its getting real hard to get new parts for the 45's.. Mine are now a custom ktm 45 marzochi magnum. Certain year KTM 45's got the dreaded "slot" and some got metered holes in the compression side. I converted the slot to the holes as per Drew Smith. it worked well! would rather have the 50's anyday!!

 

[farmerj]

Ok, a couple more questions while this topic is still "alive."

1. If you did put a CB'ed engine into a newer frame, do you also use the newer CDI or other ignition components, or change back to the older style? I'm guessing the "ignition maps" are different?

2. How would a newer "balanced" engine compare to the old CB engine? Would balancing remove some of the mechanical engine noise and quiet things down? I assume the power characteristics of the engine would stay the same?

(I'm a bit ignorant on the subject. I think I understand that you can have the crank balanced and the cases "matched"? or "machined"? - someone educate me here!)