sportsman yamaha issue

patrick slattery · Posted: Thu Sep 20, 2012 4:16 pm Post subject: sportsman yamaha issue

We were at the New Castle Man Cup last week (Man Cup), the last race, running mid 1.16, not superfast but better than earlier in the week. About 7 laps in, the kart starts slowing down, to a worse lap at the end of 18.9, the rpms drop 1000 from earlier, mph drops 5 mph and my driver is still trying to run fast, not laying off. The engine maintains a constant temp of 365 so not over heating. My question would be have you seen a kart fall off that much from start to finish? We ran the same air pressure the previous heat, and got our fastest lap on the last lap. I have a hard time believing the kart tightening up and loosing that many rpms and time. Any suggestions?

al nunley · Joined: 13 Nov 2006 Posts: 3066

Jim Howe · Posted: Fri Sep 21, 2012 4:33 am Post subject: Track Just Got Tight

I was there at NCMP too and I can tell you all the rubber on the track affected some karts differently. That track really did rubber up and I heard of a lot of karts that just got super tight and lost time, speed, RPMs, you name it.

I'm not sure you can really do anything other than watch the conditions and take a chance on loosening things up even more. Of course, sometimes you guess right, sometimes you guess wrong.

patrick slattery · Posted: Fri Sep 21, 2012 7:29 am Post subject:

We were running mid 16.6 16.7 and then it just got slower and slower. I know when a kart starts to go away but this was to an extreme if that was the root cause.

Greg Wright · Posted: Fri Sep 21, 2012 10:24 am Post subject:

NCMP punishes you severely if you get tight during the run. Most likely the tire pressure was too high at the beginning.
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Patrick Hubbell · Posted: Wed Sep 26, 2012 9:33 am Post subject:

Are you sure it was the chassis or track condition? could have been the engine.
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patrick slattery · Posted: Fri Sep 28, 2012 7:09 am Post subject:

Patrick, upon further checking, I am not sure, but I did find an issues with the carb bolts starting to back out and It might have been that issue. The incident was exactly the same as described previously. The bolts had a stripped head and I guess they worn't getting seated as tight as needed to stay put.

Dan Haynes · Posted: Fri Sep 28, 2012 7:37 am Post subject:

We attempted our first Man Cup at NCMP in 2007 running yamaha jr. can. We were in the same boat. We were about 3 seconds off pole and running about 4 teeth more than everyone else and still didn't have enough RPM. Another of the guys we regularly run with was in the same boat and thought their engine was going away. We went back to club racing the following weekend and were running right with the guys that ran up front at the Man Cup.

So my guess is it just got really tight on you.
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