450 Single Cylinder - ANY gearbox problems?

[Kirk Feldkamp]

Hi guys,

I was wondering if any teams using 450 singles (WR450, CRF450X, etc.) have had ANY issues with gearboxes relating to excessive wear... or frankly ANY failures at all (clutch included). From my trusty racing lazyboy I see the potential for the *greatly* increased grip from two slicks (versus a knobby on dirt) to cause some gearbox problems. It would be great if some teams with experience with these motors (ETS, A&M, RMIT, SLO, Queen's, etc.) could chime in. I'm very interested to hear what you have to say!

Thanks,
Kirk

[Kirk Feldkamp]

Hi guys,

I was wondering if any teams using 450 singles (WR450, CRF450X, etc.) have had ANY issues with gearboxes relating to excessive wear... or frankly ANY failures at all (clutch included). From my trusty racing lazyboy I see the potential for the *greatly* increased grip from two slicks (versus a knobby on dirt) to cause some gearbox problems. It would be great if some teams with experience with these motors (ETS, A&M, RMIT, SLO, Queen's, etc.) could chime in. I'm very interested to hear what you have to say!

Thanks,
Kirk

[SNasello]

Hey turbo,

In '05 when we ran the single with a turbo there was numerous gearbox problems, but this was probably due to the fact we were making almost twice the torque of the engine stock. We sheared the teeth off a couple of gears and clutch wear was just horrible. This was with a Suzuki single. Im not sure of the details when they ran it without the turbo in previous years, so i cant speak for that, but the turbo gave us LOTS of problems.

[John Valerio]

more detailed version of previous post...

Engine: Suzuki LTZ-400 with 470cc big bore kit
Turbo: GT12 with intercooling
Output: 65 hp, 47 ft-lbs

We did go through a couple of clutches on the dyno. then we stacked spacers on the clutch springs to keep them from frying, but then we lost a couple sets of 5th gears (total of 8 or so sheared teeth). however, once we put the motor in the car with some stiff clutch springs all we did was break traction.

we had issues with the turbo, but for other reasons. the weakest link in the drivetrain will go first, and with us it was still the tire/ground interface, not the trans or clutch like when we were on the dyno.

[Kirk Feldkamp]

Stephan and John,

Thanks for the input!

From what I remember of talking with Bruce in '05, there were a lot of unresolved tuning issues with that motor. I have a feeling there was probably a lot of detonation occuring with the setup you guys were running. From what I remember there was a LOT of timing (50+ degrees at ~12psi) and a LOT of oil getting into the cylinder (excessive compressor seal leak). From what I understand detonation is a killer for gearboxes because the torque impulse is applied over such a short period that the resulting impact between gear teeth can be enormous. The information about the clutch is good to know. It's interesting that you were able to fail gears on the dyno but not on the track... but that makes perfect sense when you get down to it.

Has anyone else running a relatively unmodified "dirtbike" single had any problems with popping teeth off gears?

-Kirk

[Big Bird]

Hi there Kirk,

I think I wrote a bit of a thesis somewhere on the problems that we have had with our 450's. (It might have been on a thread about supercharging singles or something). Knowing how tiresome some of my posts are I couldn't be bothered reading through them all to find it.

Reliability problems as follows:
* For the first two years we ran the engine stock internally, and just developed fuel injection and our own exhaust system. The only problems we had was a starter motor issue (common to all WR450's when they first came out in 2003), shearing woodruff keys off the crank. A Yamaha update fixed that up. Other than that, the engine ran perfectly reliably. (We pretty well ran the same engine for two years, 4 comps plus a lot of testing).
* We have had some issues over the past 12 months or so, and this has coincided with some internal engine mods chasing horsepower. We blew an engine in the Oakland carpark the Wed of the Detroit comp, and this was a high-comp aftermarket piston that looks like it dropped it's skirt.
* We have had no gearbox issues whatsoever.

That is the story for the WR450. We are pretty chummy with the lads from Tokyo Denki, and aside from some starter motor issues they have with their CRF450 I think that thing has been running pretty reliably too.

I think if you run the things pretty standard they are a nice and reliable little unit. If you try to wring every last bit of performance out of them then you are going to start pushing the limit and breaking things. But if you choose a little single and then try to compensate for the performance drop, then I think you have missed the whole point anyway.

As an aside, we had our first 2007 team meeting last night. Quite a few of the lads are now keen to try a 250 single and see how that goes. Might be insanity, but we reckon it could be enough - and it would be nice and easy to drive. Given the WR450 and WR250 pretty well fit in the same chassis it would be a simple retrofit for us to find out. We'll keep you posted.

Hope that helps.

Cheers,

[terra_dactile]

Hi Kirk,
We have had many issue with the gearbox, however this coincide with fact that we get demo motors from yamaha, the equivalent condition of a rental car(they really get treated bad and abused). On the dyno we have destroyed fifth gear, on the track the 2nd gear seems to wear very fast, could be our final drive ratio that makes it take a good beating.
Our motor is the WR450F From yamaha, we also had the woodruff key shearing problem mention by the Honorary Fellow from RMIT (Big Bird)

The other issue we have had with motor relate to reaching the speed limit of the springs, for some reason the valves decided they wanted to join forces with the piston,not a very friendly pairing!

Other than that just make sure that your dyno setup runs in a gear that is usualy meant to see the torque you are passing threw it.

I am not the engine guy but saw first hand the results of the aformentioned difficulties, come see us in Detroit this summer and we can show you some of the broken parts.

Jude Berthault
ETS FSAE 2003-Current
Vehicle Dynamics Leader

[JerryLH3]

We had no problems with the gearbox in our Cannondale single cylinder last year. Our main issue was a charging issue, but that's another story.