Clutch help PLEASE

[RapKor]

OK here it is, we have 1 more race left, took a 2nd and a 2nd today for a second overall, not bad but should have could have won if my rider wasn't 12 bike lengths behind the leaders going into the first turn. After the bike gets going it is a rocket! He was able to make his way to the leader in each moto and both motos he just ran out of time.
Bike runs real strong it's a Kool Kids built 08 DRR 90 l/c ported and polished,stock 08 gearing, Keihn 24 mm carb 120 main and 42 pilot,we are running the stock clutch (YAMASIDA)with a 1500 ztr torque spring (brand new every race), red malossi clutch springs and 4.0 and 4.5 gram rollers staggered(also new) with the 787 belt ( 3 races on it).
Heres the problem, bike is dead *** slow for the first 20 feet then it's a rocket but unfortunatley that first 20 feet is terminal! It is almost like the clutch slips or doesn't grab when it first engages. We have 1 mini race left in our careers as we are moving up to the 200 class next year, would love to win our last race. Need some help getting this thing dialed in I will say that the clutch shoes looked quite worn and I did not notice this until I tore it down Friday nite to do the final race prep, I usually scruff the variator with a scotch brite and I hit the shoes with some sand paper to scruff em a little. Could this be my issue? I am definatley going to change the clutch but not sure what too get, do not want to spend too much as it is our last race. Any suggestions on what else it could be? I would really appreciate any help Thanks!

[selbygirl]

did you try lighter roller wgts a few years back wen my boy was on a 50 i had 3.0 gram during a race i took a 1/8 drill bit and put several holes in the rollers made the rollers 2.8 gram and sanded the drilled hole edges to make smooth good luck tommy

[greenmachine70]

pm'd

[cik orange]

sounds like your bike is shifting to fast. but need a little more info is it reving up fine just not engaging or bogging down and gradualy building speed?

[RapKor]

It is reving fine seems to just take a second too engage almost like the clutch is slipping????. The motor pulls real strong and revs great, best plug read I have ever had with this motor, sounded great coming through the sweeper corners. My rider stated that the machine did not bog just seemed to hesitate for a second when the gate dropped. Thanks i appreciate the help!!

[cik orange]

ok if it is reveing out fine buy dr pulley hit clutch or malossi delta and a new belt. if this is not in your budget get a new yamasida rear and belt (just 10 thou wear of a belt is huge) and go up 1 or 2 teeth in the rear if your kid is cathing them at the end of a run your not getting there fast enough (gearing to high). i sent you a pm

[selbygirl]

is like a dead spot at start off in the motor we had 70 motor do that it was dogging at the start but ran good if you pin it. it was low compresion in the motor some peaple say bad crank seals do it also it only takes a second to chek your comresion did you check your roller wghts you sed you had 4 gram wghts just put 5 of them in see if it helps if it does get some lighter ones good luck tommy

[RapKor]

Compression is good, fairly new top end 1 race on it ( well 2 now) but I did check and it was same as when I finished re build. Almost seems like the bike almost has to over rev before the bike takes off. Really hard to explain but it is like it revs and grabs but really gets a hit and grabs 20 feet into the run almost like a delayed reaction. Somone suggested that there is a pressed together shaft in the transmission that the sprocket mounts too that maybe slipping?? Does this sound possible? Have never been in the tranny on this bike or any other 90 for that matter. What ya think? Going to try a new clutch soon but I am hesitant to run something different then the Yamasida as I know that one pretty well. Like I said in earlier post this is a new issue. Thanks again.

[qcitytile]

I would bet the rollers are a little heavy. Had the same issue with a motor last year. Flat on the lunge then would go like crazy. Maybe check slipper sprocket if you have one.

[greenmachine70]

Dr Pulley

[selbygirl]

did this happen wen you put your new sping in sounds allmost like a weak spring but i have seen peaple weld the tranny gear to keep from slipping; cvt"s are like women if you can under stand them your a better man then me good luck tommy

[EthansDad]

what selbygirl is saying is on track with the rollers. try that "take one out trick" - does the dead spot go away (launches in the first 20 feet like a champ), but runs out of speed at about 50-75ft? then your rollers (as they are now) are too heavy. try dropping down in 1/4g increments until you find your sweet spot.

-EA

[bulldogfallon]

Can you provide more definitive info such as RPMs of the clutch engagement or when it starts and stops pulling, Max rpm

You could have various issues

Clutch engagement could be too high or low
- allowing the quad to shift before your clutch is engaging
- engaging below the pipe/porting power range

Roller weight could be off
- Too heavy can generate flat spots on the bottom with acceleration out at small distance as you describe
- Heavy rollers will also show themselves at a long distance after the pulleys finish their shift the motor will take back over and pull hard again while the rpms increase a good amount (provides false belt travel readings and is not usable speed at desireable distance)


Lightening the rollers can help show a direction of the fix, but really the roller's job is set how fast the CVT shifts, but changing their weight also affects other areas. (like stall)

So it could even be a variator spacing issue ? If the you lowered the rollers it would increase your stall and could make it appear to be fixed, but let each component do it's job

--Lowering the rollers may help the bottom, but hurt the top, so did you really fix anything? (hypothetical example) since rollers dictate shift speed you could lose pull elsewhere.

I often find that tuning is done without letting each part of the CVT due it's assigned job....it can work, but can cause inconsistent results

If your clutch/belt is worn it could contribute to your issue like Cik Orange mentioned. (He is an excellent cvt tuner by the way, so I would listen when he offers info) :)

CVTs can be a challenge...I would recomend calling your dealer and having them talk you through it, but a tach is really needed to let the quad talk to you....communication is a must!!

Really a lot of info to be discussed on a thread, but if you get a tach and can share that data you may find your solution much faster.


A CVT is like riding a 10 speed (but more variable speeds)....You peddle at a preferred rate (where you can push it comfortably w/o lugging) while you are able to gain speed....

If rollers are too heavy it is like you shifting before you get to your comfort peddline zone which causes you to lug and not to pull and accelerate at maximum efficiency.

Too light of rollers is like peddling w/o switching the gears so you put forth the effort, but don't have ther gear ratio to go faster...lots of effort with poor results

I hope that quick simple description helps....



Good luck

[Hetrick Racing]

Just so you know my dad(Rich)is starting a class for mechanics or parents and also a dvd on clutch tuning and diagnostics.

Joel

[fomospede]

Originally posted by Hetrick Racing
Just so you know my dad(Rich)is starting a class for mechanics or parents and also a dvd on clutch tuning and diagnostics.

Joel
while making video and or giving the class please show prefered methods of venting or anger managment techniques:rolleyes:

[fomospede]

Originally posted by bulldogfallon
Can you provide more definitive info such as RPMs of the clutch engagement or when it starts and stops pulling, Max rpm

You could have various issues

Clutch engagement could be too high or low
- allowing the quad to shift before your clutch is engaging
- engaging below the pipe/porting power range

Roller weight could be off
- Too heavy can generate flat spots on the bottom with acceleration out at small distance as you describe
- Heavy rollers will also show themselves at a long distance after the pulleys finish their shift the motor will take back over and pull hard again while the rpms increase a good amount (provides false belt travel readings and is not usable speed at desireable distance)




Lightening the rollers can help show a direction of the fix, but really the roller's job is set how fast the CVT shifts, but changing their weight also affects other areas. (like stall)

So it could even be a variator spacing issue ? If the you lowered the rollers it would increase your stall and could make it appear to be fixed, but let each component do it's job

--Lowering the rollers may help the bottom, but hurt the top, so did you really fix anything? (hypothetical example) since rollers dictate shift speed you could lose pull elsewhere.

I often find that tuning is done without letting each part of the CVT due it's assigned job....it can work, but can cause inconsistent results

If your clutch/belt is worn it could contribute to your issue like Cik Orange mentioned. (He is an excellent cvt tuner by the way, so I would listen when he offers info) :)

CVTs can be a challenge...I would recomend calling your dealer and having them talk you through it, but a tach is really needed to let the quad talk to you....communication is a must!!

Really a lot of info to be discussed on a thread, but if you get a tach and can share that data you may find your solution much faster.


A CVT is like riding a 10 speed (but more variable speeds)....You peddle at a preferred rate (where you can push it comfortably w/o lugging) while you are able to gain speed....

If rollers are too heavy it is like you shifting before you get to your comfort peddline zone which causes you to lug and not to pull and accelerate at maximum efficiency.

Too light of rollers is like peddling w/o switching the gears so you put forth the effort, but don't have ther gear ratio to go faster...lots of effort with poor results

I hope that quick simple description helps....



Good luck
Gary and all the other guys are great, but without a tach you will never be the guru, it is the most important tool it can show you spring fatigue prior to a loss or worse a dnf :) :) :)