Dirtbike engine in quad frame.. Vibration?

[hondafox440]

How come everyone says dirtbike engines will vibrate more in a quad frame? Assuming you mount it in the same way wouldn't it be the same as the bike? How come the 400EX, which is based on the XR400 engine doesn't vibrate that much, and the same with the YFZ440? Is it because of the lack of lateral (side to side) movement due to the 4 wheels?

[Juggalo]

most dirtbike engines don't have counterbalancers in them. thats why engines such as the CR250 and CR500 vibrate more. on a dirtbike the forks absorb most of the vibration.

[hondafox440]

Bump. Any other opinions?

[dirtmomma]

I'm curious does a 4 stroke motor vibrate as much as a 2stroke in a quad frame?? We are putting a XR600 in a frame, it was going to be a 250r but it's not straight:rolleyes: so now we're on the lookout for a cheap 400 frame.

[StreetLegalEX]

I think most 4strokes are counter-balanced, 2strokes usually not.

[spud400ex]

fisher cycle (i think) built one with a cr250 and said that the vibration wasnt very bad.

[BullySpeedFreak]

I;m buildin a 92' 250x with a 95 250exc motor and made some rubber washered motor mounts, and this motor was counterbalanced, so I should be all set on the vibration depo

[BullySpeedFreak]

I;m buildin a 92' 250x with a 95 250exc motor and made some rubber washered motor mounts, and this motor was counterbalanced, so I should be all set on the vibration depo

[bmw500hp]

anybody out there do a cr500 motor in a 250r frame....a bud found one (motor) and wants to try the conversion?? :)

maybe a few tips or suggestions for him!!

[pnut420]

I would think it would be doable, chef was running a PV425 in a 250r frame, Im sure it was gussetted and all that, but if done right it should be ok.

[310Rduner]

Originally posted by pnut420
I would think it would be doable, chef was running a PV425 in a 250r frame, Im sure it was gussetted and all that, but if done right it should be ok.

Yes, but his engine is a counterbalanced R; not an un-counterbalanced dbike..

425Pv is just a big bore top end, it isn't from another type of bike.

[Chef]

Originally posted by pnut420
I would think it would be doable, chef was running a PV425 in a 250r frame, Im sure it was gussetted and all that, but if done right it should be ok.

Its a 250R motor with a 425 cylinder.;)

[hondafox440]

What exactly is a counterbalancer? I still can't believe that the bike engine will vibrate that much more. Seems like a big urban myth to me.

[pnut420]

Originally posted by Chef
Its a 250R motor with a 425 cylinder.;)

I know but its still alot of torque also, maybe not as much vibration but hell its pushing what 90+hp?

[pnut420]

Originally posted by hondafox440
What exactly is a counterbalancer? I still can't believe that the bike engine will vibrate that much more. Seems like a big urban myth to me.

Nah man its no myth, really though if you think about it a KX125 dirtbike does vibrate like crazy, but the forks take the vibration alot better, plus the frame is alot narrower making the ditbike frame stronger

[hondafox440]

I couldn't see a 425 2 stroke pushing anymore than 70HP. Eric Gorr built a CR500 bike, fully pimped and it was right around 75HP. For those of you that don't know Eric is one of the most respected engine builders and I believe he used to wrench for Kawasaki. If you ever need head work done on a 2 stroke this is the guy to have do it. http://www.ericgorr.com .

[hondafox440]

Originally posted by pnut420
Nah man its no myth, really though if you think about it a KX125 dirtbike does vibrate like crazy, but the forks take the vibration alot better, plus the frame is alot narrower making the ditbike frame stronger

That doesn't make sense. If the forks absorb the vibrations why doesn't the front suspension on the quad do it? With 3 shocks you would think it would absorb MORE of the vibration.

[Chef]

Originally posted by hondafox440
I couldn't see a 425 2 stroke pushing anymore than 70HP. .

I suppose you've never been around PSI's 10 port Genesis R stuff then?

[pnut420]

Originally posted by hondafox440
That doesn't make sense. If the forks absorb the vibrations why doesn't the front suspension on the quad do it? With 3 shocks you would think it would absorb MORE of the vibration.

The forks pretty much act as two shocks but are 1 piece, also a dirtbike is much lighter than a quad so the first 3 inches of travel are going to be much softer than a quads would be, and dirtbikes come factory with alot more travel than a quad.

[310Rduner]

Originally posted by hondafox440
I couldn't see a 425 2 stroke pushing anymore than 70HP. Eric Gorr built a CR500 bike, fully pimped and it was right around 75HP. For those of you that don't know Eric is one of the most respected engine builders and I believe he used to wrench for Kawasaki. If you ever need head work done on a 2 stroke this is the guy to have do it. http://www.ericgorr.com .

http://www.localgeographic.com/pictures/P-56.gif

[hondafox440]

I'm stupid now? STFU and show me some dyno charts.

[pnut420]

Originally posted by hondafox440
I'm stupid now? STFU and show me some dyno charts.

That wasnt cool of him calling you stupid, but dont be ignorant, Chef will privide you with some dynos and prove you wrong, so we will STFU and get some charts if you really need them:rolleyes:

[nacs400ex]

I believe Chef, can you not belief it without a dyno? Take his word, why would he have a reason to lie.

[nacs400ex]

Originally posted by 310Rduner
http://www.localgeographic.com/pictures/P-56.gif

So true. :p

[pnut420]

Originally posted by nacs400ex
I believe Chef, can you not belief it without a dyno? Take his word, why would he have a reason to lie.

Yeah but be calling out the CHEF :eek:

[Juggalo]

sparks built a 400ex that had 90 somethin horsepower for the 4 stroke wars.. pretty good huh?

[Chef]

Originally posted by Juggalo
sparks built a 400ex that had 90 somethin horsepower for the 4 stroke wars.. pretty good huh?

Are you talking about last years FSW 400? That bike didnt have 90 horsepower. It was just extremely light. It was probably mid to high 60's for horsepower, with a 115 lb rider. No battery, no starter, no front bummper no lights, it was just as bare as they could make it.

I dont have dyno results, but judging by it pulling the front wheels at the top of 6th gear I think its got more than 70hp.

[hondafox440]

I'm not saying he is lying. I'm sure his bike puts down a good amount of power. 90HP is A LOT of horsepower. Thats more than some cars. Look at the Honda CR500 dirtbike. If you have ridden one you know they are SCARY fast. Easily wheelies in the highest gear, stock. They are only 55HP.

Does your 425 run on alcohol or gas? The CR500 that Gorr built ran on 50/50 pump gas/race gas. With alcohol and/or nitrous 90HP is not far fetched. I was referring to gasoline engines.

A stock 250R is what, 30HP? So basically double the displacement , +20HP. Pipe/silencer, +5HP. Head work, porting, higher compression, +10HP. A larger carb to feed it all, +3HP. Thats 68HP, all with rough estimates so I have no idea if it is correct or not, but it seems reasonable. Again, alcohol/nitrous will obviously affect it.

[310Rduner]

Originally posted by hondafox440
I'm not saying he is lying. I'm sure his bike puts down a good amount of power. 90HP is A LOT of horsepower. Thats more than some cars. Look at the Honda CR500 dirtbike. If you have ridden one you know they are SCARY fast. Easily wheelies in the highest gear, stock. They are only 55HP.

Does your 425 run on alcohol or gas? The CR500 that Gorr built ran on 50/50 pump gas/race gas. With alcohol and/or nitrous 90HP is not far fetched. I was referring to gasoline engines.

A stock 250R is what, 30HP? So basically double the displacement , +20HP. Pipe/silencer, +5HP. Head work, porting, higher compression, +10HP. A larger carb to feed it all, +3HP. Thats 68HP, all with rough estimates so I have no idea if it is correct or not, but it seems reasonable. Again, alcohol/nitrous will obviously affect it.

dude.. stop talking before you get laughed at please. That is some sad logic and reasoning right there
:huh

[Chef]

Originally posted by hondafox440
I'm not saying he is lying. I'm sure his bike puts down a good amount of power. 90HP is A LOT of horsepower. Thats more than some cars. Look at the Honda CR500 dirtbike. If you have ridden one you know they are SCARY fast. Easily wheelies in the highest gear, stock. They are only 55HP.

A stock 250R is what, 30HP? So basically double the displacement , +20HP. Pipe/silencer, +5HP. Head work, porting, higher compression, +10HP. A larger carb to feed it all, +3HP. Thats 68HP, all with rough estimates so I have no idea if it is correct or not, but it seems reasonable. Again, alcohol/nitrous will obviously affect it.

Look at the ride height on the CR500 bike. Ride height has alot to do with wheelies and weight transfer. The front of the frame on my R is 5 inches from the ground. That makes a big difference. It leaves blackmarks for about 60 feet with 11inch wide Hoosier TT tires.

My estimates of mid 80 to high 80's or low 90's is judging from a ATC with a 425 and a drag port. That bike was dynoed at 112 hp. I dont see myself losing 40hp from a TT port.

[pnut420]

Originally posted by 310Rduner
dude.. stop talking before you get laughed at please. That is some sad logic and reasoning right there
:huh

:blah: Yah just let it go man. Noy only does a dirtbike ride higher, it is way lighter, their is nothing to the front end of a CR500 compared to the front end of a TT quad, do you have any idea how much weight those quads have up front. Just let it go man....

also Chef has Billet Aluminum head that are completely aftermarket, so your hp figures are sooooo far off. Add another 20 hp in their and you will be alot closer ;)

[wilkin250r]

I'm not going to jump into a pissing match about HP numbers, but to answer the ORIGINAL question:

With the design of dirtbike frames, the vibration from the motor doesn't travel through the handlebars quite as much as in a quad frame, because its only attached at one point (the forks) where a quad frame is attached at two places through the steering stem. Plus, since the dirtbike frames are smaller, you can make them stronger and they will still be lighter than an ATV frame. These factors combined, the vibration isn't nearly as big a deal in a dirtbike frame as in a quad frame.

I knew a guy that put the CR500 motor in a 250r frame, and he says it was the worst thing he's ever ridden. Yes, lots of power, but the vibration made his hands go numb. In the long run, the vibration was constantly breaking the welds on the motor mounts every couple weeks, even with rubber engine mounts.

So yes, vibration is a REALLY big deal in a quad frame, but not so much in a dirtbike frame.

Also, to answer your question about "What exactly is a counterbalancer?"

Imagine you have a propeller with two blades, spinning. If one of those blades breaks off, the other blade creates a vibration because it becomes a mass spinning off-center. This is the same principle. The mass of the piston traveling up and down will cause a vibration. The counterbalance is an off-center mass driven off the crankshaft. When the piston goes up, the counterbalance goes down. This creates a vibration exactly opposite the piston, and the two cancel each other out.

[hondafox440]

Here is a dyno chart of a 250R with full porting done (if you read some tech articles on his site you know this guy knows what he is doing). http://www.macdizzy.com/trx_dyno.htm "Peak SAE corrected HP as measured at the rear wheel is 53.3 with the high compression head and 49.7 with the lower compression head."

I just can't imagine getting another 40HP out of it just by boring/stroking it. I'm not bashing you Chef, I'm sure your R is fast as hell and I know how much time and money you put into it. It is definitely one of the nicest R's I have seen. I'm just trying to have an "adult" debate but it seems that some people (310R and pnut) can't do that and need to resort to the 6th grade tactics of making fun of people.

Wilkin - Thanks for the explanation. Makes sense now.

[hondafox440]

I also just found this.

From http://www.4x4tuff.com/proddetail?catid=29&prodid=161 , right near the bottom.

"425cc OF INCREDIBLE TORQUE & HP:
This kit is truly the ultimate in power and torque. It has over 70HP and the powerband of a 520 KTM 4-stroker, all blended together in one beautiful package. In its' debut race at the Orville, OH Pro National in July it won the TT National by over a half a lap and was piloted by Darrel Rath from Minnesota! Wow!!

This kit uses the same hardware package as the 250/330 kit, but uses a larger volume exhaust pipe and silencer kit and a different cylinder - very tractor like torque for maximum power potential . Yet it has the ability to rev quick and supply you the ultimate in acceleration and speed. This 425cc cylinder kit uses a 86mm piston that is ceramic coated on top and poly-moly on its side for long life in its Nikasil bore. It also uses a large bore "Dial-A-Dome" head with its' exceptional cooling capacity and easily adjustable chamber for the different fuels that may be used. See 330cc kit for fuel recommendations. This kit does come complete with a V-Force Reed cage, aluminum intake manifold with a matching rubber boot and a heavy duty head stay. All billet water manifolds, o-rings and gaskets are supplied with this unique 10-Port Genesis Cylinder. This kit does require a case mod for the piston to fit and it also get's a couple of extra boost ports added to the case. This case mod generally can be turned around in few days or quicker if necessary to meet a race need. A few of our customers with machine shops have done their own case mod with our instruction sheets. Please inform us of your interest on the machined case process."

[Juggalo]

the ex i was talking about, i just heard about from some guys that were like some of the promoters of FSW. i dunno if they were lyin or estimating or what.

[pnut420]

Originally posted by hondafox440
Here is a dyno chart of a 250R with full porting done (if you read some tech articles on his site you know this guy knows what he is doing). http://www.macdizzy.com/trx_dyno.htm "Peak SAE corrected HP as measured at the rear wheel is 53.3 with the high compression head and 49.7 with the lower compression head."

I just can't imagine getting another 40HP out of it just by boring/stroking it. I'm not bashing you Chef, I'm sure your R is fast as hell and I know how much time and money you put into it. It is definitely one of the nicest R's I have seen. I'm just trying to have an "adult" debate but it seems that some people (310R and pnut) can't do that and need to resort to the 6th grade tactics of making fun of people.

Wilkin - Thanks for the explanation. Makes sense now.

I didnt bash you, I even gave you an explanation about why the dirtbike can take all the vibration from the dirtbike engine, but a quad can't. And then you said quite a few things that you pretty much made yourself look silly on. :confused:

[pnut420]

Originally posted by hondafox440
Here is a dyno chart of a 250R with full porting done (if you read some tech articles on his site you know this guy knows what he is doing). http://www.macdizzy.com/trx_dyno.htm "Peak SAE corrected HP as measured at the rear wheel is 53.3 with the high compression head and 49.7 with the lower compression head."

I just can't imagine getting another 40HP out of it just by boring/stroking it. I'm not bashing you Chef, I'm sure your R is fast as hell and I know how much time and money you put into it. It is definitely one of the nicest R's I have seen. I'm just trying to have an "adult" debate but it seems that some people (310R and pnut) can't do that and need to resort to the 6th grade tactics of making fun of people.

Wilkin - Thanks for the explanation. Makes sense now.

Not only do you have 425cc instead of 250cc, he had some of the trickest heads out there. The 425cc will also allow a bigger carb to be used and a larger exhaust, etc... Its not just the bore that gives an extra 37hp.

[pnut420]

Originally posted by hondafox440
I'm stupid now? STFU and show me some dyno charts.

You also had the 6th grade rebound yourself buddy.

[310Rduner]

Originally posted by hondafox440
Here is a dyno chart of a 250R with full porting done (if you read some tech articles on his site you know this guy knows what he is doing). http://www.macdizzy.com/trx_dyno.htm "Peak SAE corrected HP as measured at the rear wheel is 53.3 with the high compression head and 49.7 with the lower compression head."

I just can't imagine getting another 40HP out of it just by boring/stroking it. I'm not bashing you Chef, I'm sure your R is fast as hell and I know how much time and money you put into it. It is definitely one of the nicest R's I have seen. I'm just trying to have an "adult" debate but it seems that some people (310R and pnut) can't do that and need to resort to the 6th grade tactics of making fun of people.

Wilkin - Thanks for the explanation. Makes sense now.

That is only a 66mm bore R...and you are saying that an addition 175cc's won't make up another 40hp when combined with all that goes into the kit? Look at how much additional cooling capacity it has than the macdizzy motor that Rick built that makes 50hp. Plus the double pass radiator, the huge portwork that goes into it, the large carb, sheer size and just as you have shown above the TALENT of the person who made it.


If you want to have an adult debate, then I'll get a little more serious with you. If you question my abilities at carrying on an adult conversation, then go look at a few of my posts in the Religion thread, and you'll be proven wrong. At the time, I just felt like making fun of your sad logic there, and so I did because you are pretty far off.

[hondafox440]

I'll admit I made some stupid and statements with no backing, but I didn't bash anyone.

And I know that displacement doesnt just add horsepower. However, if you have 2 motors with very similar port work, intake and carburetion, and exhaust, displacement becomes a factor. And cooling capacity should have no effect on a dyno run because the motor doesn't get hot enough for heat loss to becore a measureable factor. Even if it did, we are talking about 1-3HP.

Chef, could you give some specs on your motor? Such as port work, what model pipe, which carburetor, compression ratio, bore/stroke? I assume it is close to that 2nd link I posted (the one to the 425 kit), in which case your motor would be close to 70HP (more depending on intake/exhaust).

Another factor that comes in is rideability. Even if one did build a 90HP sub 500cc 2 stroke engine, how rideable would it be? Chef's machine obviously has a broader powerband and is not built solely for drag racing. If one did achieve 90HP out of a 500, chances are it was built with one thing in mind - peak HP (Hmm, CR125 anyone?).

Another thing, where are you measuring HP? I am talking about RWHP, not bHP.

[Chef]

Originally posted by hondafox440
Chef, could you give some specs on your motor? Such as port work, what model pipe, which carburetor, compression ratio, bore/stroke? I assume it is close to that 2nd link I posted (the one to the 425 kit), in which case your motor would be close to 70HP (more depending on intake/exhaust).


Bore: 86mm
Stroke: Stock (??)
Carb: Keihin 39
Compression: 195 lbs
Porting: PSI TT/Drag port. Triple Exhaust Port, 2 extra boost ports, etc.
Lightened: Crank, CR250 Flywheel, Piston, Rod.
Exhaust: PSI Hi-Volume TT Pipe + Silencer
Reeds: V-Force II Carbon Fiber.
Intake: PSI Custom
Powervalve: PSI V.E.P.

The intake manifold was matched to the reed cage, because it wasnt a smooth transition between the two. The intake manifold was a smaller I.D. than the reed cage. No airbox used. VP Ultimate 2 was used (6% more hp across the range) The ports had to be cleaned up because PSI did a chitty job.

Pic of my intake vs stock intake \/

http://pictureposter.allbrand.nu/pictures/Chef/PSI%20Vs.%20Stock0001.jpg.jpg

[pnut420]

Even if one did build a 90HP sub 500cc 2 stroke engine, how rideable would it be?

Dude do you know what a yamaha banshee can do with 500cc? Ive seen people cut the engine between the 2nd cylinder on two different blocks, making it a three cylinder, crazy amounts of horsepower can be made with smaller displacement it just takes some $. And how rideable would it be, well if you are doing TT or sand drag, uphill climps it would be very usable.

From the get go I was just saying if chef has 90 horsepower, even 70hp I thought it would be possible to put the cr500 in, but after I was told the cr500 does not have a counterbalncer I zipped it. Then you are all no Im having a stubborn time believing that he is pushing 90hp, blah, blah...

[Jeff Marcucci]

Guys,The main reason a counterbalancer is used in a quad engine is to help keep the engine turning under braking and when using the clutch. See under these conditions with two rear tires of a quad the engine would stall. The counterbalancer ads weight to the rotation parts conected to the crank. A CR500 works as a direct bolt in in a quad because of it's heavy crank. A dirt bike with such a small contact patch will not drag down the engine. As for vibration it does ad to reduce vibration but that's not is sole purpose. Example: car guys cut the flwheel on the four cylinders to make them rev quicker but the have a harder time getting them off the line without stalling them. A flywhell keeps a engine running at low speeds.

[Juggalo]

Originally posted by Jeff Marcucci
Guys,The main reason a counterbalancer is used in a quad engine is to help keep the engine turning under braking and when using the clutch. See under these conditions with two rear tires of a quad the engine would stall. The counterbalancer ads weight to the rotation parts conected to the crank. A CR500 works as a direct bolt in in a quad because of it's heavy crank. A dirt bike with such a small contact patch will not drag down the engine. As for vibration it does ad to reduce vibration but that's not is sole purpose. Example: car guys cut the flwheel on the four cylinders to make them rev quicker but the have a harder time getting them off the line without stalling them. A flywhell keeps a engine running at low speeds.

that doesn't make sense. like you said the flywheel keeps it from stalling. thats not the counterbalancers job. quads usually have heavier flywheels than bikes anyways, to help with the problem you mentioned above but when you brake you normally have your clutch in anyways and that would not stall a motor. the counter balancers main function is to reduce vibration not to prevent stalling. the CR500 is a bad idea. when i had my LT i sheared the counterbalancer off the key and when i rode it without it that thing vibrated like a mofo. in fact it snapped the frame in 2 places. that was on a 250, i couldn't imagine the vibration on a 500. by the way it wasn't any easier to stall without the counterbalancer either.

[wilkin250r]

The counterbalance does add rotating mass, and thus will help keep the engine rotating and prevent it from stalling, but that's certainly not it's main purpose, that purpose is already served by the flywheel. The main reason for the counterbalance is, just as it's name implies, to counterbalance the vibration caused by the piston.

This is why several companies offer services to lighten the flywheel, to decrease the rotating mass and allow the engine to rev faster (the downside is, the engine will stall easier)

If you were to lighten the counterbalance, you would throw off the vibration of the engine.

Personally, I would like to see counterbalance weights, to offset the vibration of a larger piston from an aftermarket big-bore kit. However, the amount of research involved with counterbalance weights would be incredible, so I'm not likely to see them offered as an aftermarket accessory.

[pnut420]

Yeah people shave their flywheel, not the counterbalancer, thus showing the flywheel is the main thing that keeps it rotating :cool: