V Twin advice pls read

[Beamish]

http://www.hondavtrsp.com/viewtopic.php ... highlight=

I've got a, I hope, minor problem with my race tuned Firestorm engine which I'm asking Roger Ditchfield to help. He said the following, which made me forget to breath. His response to my intro regarding my engine issue, in caps

"I took it to a track day (the Californian SuperBike School) and it was good, stronger than standard, but the flat spot was very noticeable, (mostly because we were doing drills lapping the track (stowe circuit) in 3rd with no brakes - accelerating out in 3rd sometimes made the 4-5K flat spot really obvious).

Roger: NEVER TAKE PART IN THAT "3rd GEAR - NO BRAKES" SESSION AGAIN.
I HAVE REBUILT FOUR VTRs THAT ALL SNAPPED THE FRONT CONROD JUST UNDER THE LITTLE END THROUGH "PISTON WHIPLASH" ALL FROM THE CALIFORNIA SUPERBIKE RACE SCHOOL.
ONE OF THESE BIKES I COLLECTED FROM THE SCHOOL ITSELF. AT THAT TIME I SPOKE AT LENGTH TO THE GUY WHO RUNS IT (FORGOTTEN HIS NAME NOW) AND EXPLAINED HOW THE PROBLEM IS CAUSED BY THAT TYPE OF SESSION. I ASKED HIM TO ADVISE ALL "V" TWIN OWNERS NOT TO PARTICIPATE IN THAT PARTICULAR SESSION. OBVIOUSLY HE HAS NOT TAKEN MY ADVICE."

I did ask Andy Ibbot if I could use 2nd, but he said no, as we didn't have the throttle control.....Holy sh!t...advice to all Vtwin users......

Most of you will know about mr Ditchfield so it appears to be a genuine problem.

[WireWalker]

It certainly doesn't sound good does it? Though I wonder at the phrase "Race Tuned" and how much of an effect that had on the situation. I have heard that after 145bhp even the mighty SP gear drive can fail horribly, the gearboxes apparently "Turn to chocolate" was the phrase used as I remember and the letting loose of the front piston was another common issue so it's really only a few horses difference between bombproof and bomb!

[gilson]

I spoke to Roger (about some work to the engine) and he only has evidence that this has happend to 4 VTRs and 1 SP1 on this very exercise. He explained it to me as whiplash. As the engine is not being revved, the crankshaft is spining faster than the conrods making it all loose. When you then accelerate, the power snaps in and the whip then snaps the conrod just under the eye of the piston. He's seem thousands of VTR engines and only seen these 4 engines with this particular damage, all from this specific exercise.

He would think that this could be likely for all V-Twins, although has never seen it in any other engine, but that doesn't mean that it doesn't exist though.

Just be careful really, and if it were me, even though they said 3rd, I'd be in second and roll on the power gently.

Very interesting.

[sirch345]

Interesting indeed

So it seems doing these laps in 3rd gear only, using the engine only for braking, is what's causing this (in a very small numbers) to happen!

Chris.