drr 50

[dgmiller]

i am NEW to these machines and i am totally lost. i bought my son a 2006 drr 50 with a chris grissum ported head and cylinder it also has a after market carb on it with some ignition upgrades. when i bought drr the previous owner told me i need some new clutch parts so now my question is i'm wanting to get a hetrick gen 2 pipe and new clutches, reed valves, rollers and any other parts i need? i've already talked to hetrick racing about the parts thats where i plan on buying the parts just want some insight on what to buy. thanks

[JIM GRACE]

Our first race quad wAs a 06 drr 50. We had a lot of success with stock ( yamasida) clutches and variator's. The next best thing would be a Stage 6 adjustable clutch. I am sure a lot has changed in the past 4 years.

If you are running the production class that allows mods then the sky is the limit.

Hope this helps, you can pm me also with ?

[dgmiller]

yes he will be racing in the production class of the IATVHSS.

[EthansDad]

Hey miller -
what size carb is on that? 16mm, 20mm, 21mm?

do you happen to know what kind of rpms you machine is turning on the ground? likely in the range of 10-12krpms I'm guessing.

what's your design goals? mx, TT, trail?

The reason you will need new clutching is your engine mod parts will move the power curve around and your clutch needs to be mapped up with that or its wasted money in the motor mods.

don't know your motor, so some general thoughts on clutch parts -

yamasita variator (stock DRR) - we like it to. if you are getting more RPMs, then the job here will likely be to lower the roller weights. what are you running now? somewhere from 3.0-3.5g per weight will be a target.

belt - 780 is a safe bet, works good on the 50s. might get a bit more from a 782, may not depending on your rpms you target.

rear clutch - pulley is fine stock. the stage 6 clutch shoes and bell will allow you to move your stall speed or engagement speed around a bit. on the 50s, we like to launch at high rpms since there is no real power on bottom. it can be hard to get that from the stock clutch by just changing clutch shoe springs, although I've seen it done with the right mods. stalling at 7000-7500 rpms is a good target.

rear spring - pick one of your favs, should be in the stiffer 1000 range, or maybe in the 1500 range. a lot of folks like the red malossi for the 50s, seen others use the ztr 1000 or even the koso/max rpm in either of those ranges. you will need more spring tension to overcome the force of your clutch parts spinning faster now.

-EA

[tntauto1127]

I have a Hetrick Gen 2 for sale $60 shipped if your interested.

[dgmiller]

He will be racing XC style racing. the carb is a KEIHIN i'm guessing a 20mm. my son is also a little guy he is only 4 about to turn 5 and is only 50 lbs without gear on.

[EthansDad]

ideally, you'd want to know the RPM at which your setup makes max HP and set up your clutch to shift in that range. without knowing that, its a lot of guess work. for XC, although that is not our style, I'm guessing you'd want to have a bit lower stall RPM (easier to navigate woods at lower engagement rpms) and very good longevity of the clutch since xcs can be long. this means might want to take a little less performance for some longer life.

here would be my guess for a starting point. can fine tune from here -

max rpm / hp peak target - 12k rpm (guess)
var: yamasida
roller: 3.25
belt 782
clutch pulley: stock
clutch shoe and bell: stage 6
-using orange spring tighten to show only 3 ticks remaining - should engage at 6500-6800 rpms
torque spring: ztr 1000 or malossi red

things to try if its not right:
drop rollers to 3.0 if you are more than 12k rpms- or try 3.5 if you are less than 12k rpms
shim 1mm between variator halves to give a bit better take off (keeps it in low gear longer)
increase / decrease spring tension on stage six -try to find best engagement rpm - tighten the springs to two ticks remaining -should be around 7000 rpms engagement
drop to 780 belt

[fomospede]

pm me Carter ran and won most of the 50cc production races in the iatvhss! and glad to help
Brad

[bulldogfallon]

For such a young rider you may want a pipe that produces power in a more usable range...even a stock DRX90 pipe would be a decent choice...or even a new DRX50 pipe (Do you have a pic of the one on your quad).

Grissom's power is generally about 9,500 with DRX 50 Pipe and about 10,500 with a DRX90 pipe.

Clutching seems to like to engage around 6,200-6,500

EthansDad is providing some excellent info...he is very very good with the CVT tuning so I would absorb as much of his knowledge as you can.

Grissom ports all of our engines, so we are very familair with his work.

For woods racing you may want to keep the maxrpm down to ensure reliability and rideability.

Keep the questions coming, but be careful what pipe you choose...it has a huge effect on the 2 above mentioned characteristics

[fomospede]

they are right but
the clutch springs should be reds for longevity unless you want to take it apart all the time!
and the red hebo proved its worth over the long run as well but
a heavier roller had to be used
but most important of all vent the cover heat is the enemy of the cvt!
also they didnt mention tools needed a tach is a must for tuning and to watch for spring deterioration

[450Honda23]

I am also new to these machines. Just bought my son one for Christmas and it doesn't have much power until the power band kicks in. I that nodal for a stock machine or is there something I can do to up that..he wants to do XC but this thing won't climb very big hills the way it is. He weights about 7o lb s. any help would be great. I'm a honda guy so don't know to much about these.

[bulldogfallon]

Retune the cvt and jet the carb.

They don't come from factory with a proper set up.

We run
3.00 to 3.25 gram rollers
Kombat 1,250 torque spring
782x16 belt

Call our techline if u need more help

Good luck

[desratt]

Yea don't know how your son is but if you have no experience with these you should be looking for a new set of drawers right now. Yes believe it or not we have bought 2 that wouldn't even run till we did minor changes..