Drr slow start issues

[cudon12979]

I building a drr 50 we were testing over the weekend and it's really doggy on the start , once it picks up it's fine. This is what we have.....mhr team 50 cylinder , 21mm stage 6 carb with 150 main , 42 piolot. pvl ignition , 3.5 grams in the variator. Stage 6 85mm crank. Completely baffled , any help would greatly be appreciated.

[selbygirl]

do you have a new spring in it plus you can take out one of the rollers and see if that helps if it does lighten up on your rollers and may be your main is to fat we had a fifty motor 21 carb with a 110 main and i took 2.8 and 30 rollers and mixed them with a ztr 1500 spring and if your running a pvl make shore you have a tight fit on your plug wire and spark plug i use a zip tie to hold them tight check your spark plug color if you go with a smaller jet good luck tommy

[kfx450]

we ran 3 gram rollers in our stage 6 50 with a 1000 koso spring. Also make sure the belt isn't traveling before the clutch is engaging. We running 1000 shoe springs because we had a lot of trouble with the belt engaging too soon

[jerkyboy]

Pilot and main jets seem big.

[fomospede]

first what is your stall rpm ?
no tach buy it NOW!
i do not know what elevation or weather where you are but im in the midwest and ran a110 main jet in a 21mm carb
weights where 3.5 or3.75
also what about your timing if its off all those other thing wont fix it!

[cudon12979]

Thanks guys for all the quick replies , I'm going back too the shop to try again. I live in the northeast , still a little cold up here.

[rmuscle]

dont know how true but i was told once a 50 wouldnt run well with an 85 mm crank rod . could be wrong but we were looking into it at one time and i was told not to do it. but like i said not sure if thats true

[redonkulousruntsracing]

The "TEAM MHR" 50 cylinder is made for a 85mm crank. They run great, but it's more of a top end set up, good for TT. For MX you give up the low end with the 85mm crank. For MX you will get better low end and corner to corner speed with the OEM length 80mm crank.

And I also think it sound pretty fat on the main I would think you would want to be in the teens or low twenties. I am surprised it cleans out with that big a jet in it.

[desratt]

with the back tires off the ground does it seem fine???

[kfx450]

Which version of stage 6 21mm carb is this???

[cudon12979]

On the lift it's o.k.

[cudon12979]

It's a pwk carb

[Hetrick Racing]

The 50 is its own little beast,cant say it will work on every one but I usually run either the v-force cage or the old tin reed stock cage,With a pe 20 carb
The reversion that you will get under 6000rpm with the larger carb and reed cage is the cause of your problem 80% of the time.

If you dont have this stuff, try to stall it up around 8500 to 9000 that may help.

[desratt]

if it is fine on the lift then it is clutching. lighter rollers. and or stronger main spring

[cudon12979]

Thanks for the help on the drr , however I decided too measure the carb. 24mm not 21mm. It's been a tuning nightmare so far , seem close but then seem too far. Put a 21mm stock carb on this little beast and this is what I got.....In the mid , while on the lift it spits and sputters then clears up past the mid. Took air tube off and it ran a little better. It's timed 60 thousand past top dead center. Should I adjust the timing more or mess with the carb adjustments:confused:

[Logan #34's Dad]

Sounds like your needle is off. If it is like cutting off then back on while your holding the throttle at 1/2 then your too rich. Raise the clip (lowering the needle).

[jerkyboy]

Are you sure about the timing never heard setting the timing past TDC. Stock timing is 40 before TDC.

[fomospede]

Originally posted by jerkyboy
Are you sure about the timing never heard setting the timing past TDC. Stock timing is 40 before TDC.
im with this guy!

[Coley'sdad#8]

he caught the writing and is correct.
if your timing is set @ 60 after TDC you got problems period.
Ignition is designed to advance off throttle which would put you even farther 6 to 8 deg past where you are now which would absolutely run like a burro wearing flip flops. Settings should be BTDC = before top dead center

[Coley'sdad#8]

IF your timing is in fact set AFTER TDC I would surely do a leakdown check and check your reeds for cracks that could have resulted from incorrect timing setting.
Reason being is that your detonation / explosion is actually taking place on the "blow down" cycle and may very well still be exploding when piston gets down to the transfer ports sending the explosion into the crankcase.

[jerkyboy]

run like a burro wearing flip flops

Chris you crack me up.

[cudon12979]

Thanks for the replies , it's now running better.