Help! Before I light this little 50 on fire

[mcwilly]

'08 DRR 50 l/c. Bone stock cylinder/head. PWK 21mm carb. 110 main, 38 pilot, no wiring harness, no electric start.
About a month ago his cdi went out....was missing at all rpm's during practice. I replaced the cdi/coil and it ran great. Got two races out of it. After our last race, it wouldnt start when I was loading it onto the trailer.
Last week, it still wouldnt start. Checked for spark and I was only getting spark 1 out of every 10 or so kicks. Installed a new stator (factory mounting locations, no advance or retard in timing) and now it starts on the first kick.
But now, it's missing on the top end at WOT. I've tried jetting with no changes. I checked the reeds. Re-sealed the intake at the carb boot. Changed plugs. Used a different (good) cdi/coil off another bike and it actually ran worse with that. Used different plug cable and plug boot. Checked and re-ran all my grounds. Added two extra grounds from frame to motor with connections grinded down to bare metal.
I'm stumped and we have a race this weekend. Any thoughts?

[jvlavl]

do what i did...give up and get him a rm65. :ermm:

[EthansDad]

Two thoughts for you. First since you've ditched the wiring try an after market cdi coil combo device like the one from koso. A few more revs and less to trouble shoot.

Second, on a bone stock I'd ditch the 21mm carb and run the 16mm. I have a spare if you want to buy pm me. The 16mm is bullet proof and provides more bottom and enough top for that setup.

[EthansDad]

Two thoughts for you. First since you've ditched the wiring try an after market cdi coil combo device like the one from koso. A few more revs and less to trouble shoot.

Second, on a bone stock I'd ditch the 21mm carb and run the 16mm. I have a spare if you want to buy pm me. The 16mm is bullet proof and provides more bottom and enough top for that setup.

[quad59]

Is it staving for fuel or just cutting out, check your crank seals,dirt in the carb,float setting, electrical connections, kills switch ( stock ones suck)

[selbygirl]

check the wires going to the cdi to the coil and the ground i think its orange and the other is black the factory plug connection i took mine and hard wired it i think the connection vibrates at high rpms and gives a bad connection i seen it happin to two other bikes and check that kill switch just by passit see if that your problem seeya tommy

[Ride4ACure]

I had a similar problem..it ended up being a problem with the coil mount points..cleaned behind the mounting bolts and replaced the now intemittent coil with a new one.....it really had us chasing our tail...

[mcwilly]

Originally posted by EthansDad
Two thoughts for you. First since you've ditched the wiring try an after market cdi coil combo device like the one from koso. A few more revs and less to trouble shoot.

Second, on a bone stock I'd ditch the 21mm carb and run the 16mm. I have a spare if you want to buy pm me. The 16mm is bullet proof and provides more bottom and enough top for that setup.


Thanks for the carb offer. Actually, I have a 16mm as well that I'm trying to sell in the classifieds. I installed it and couldnt get it to work. The throttle cable was about 1/2" too short (We have the Flexx handlebars). I ran it every way possible with no luck. I could connect it to the housing but it was too tight when the handlebars were turned all the way.


Is it staving for fuel or just cutting out, check your crank seals,dirt in the carb,float setting, electrical connections, kills switch ( stock ones suck)
cutting out. Changed fuel lines and fuel filter. Checked the crank seals. I've re-done all of my electrical connections too many times to count lol. Kill switch is still one that's got me scratching my head. I've eliminated it from the equation, and when I do, it wont start. :confused:


I had a similar problem..it ended up being a problem with the coil mount points..cleaned behind the mounting bolts and replaced the now intemittent coil with a new one.....it really had us chasing our tail...
I grinded the mounts, but didnt ever clean behind it....but I will.

Thanks for the replies!

[jerkyboy]

You said you checked the crank seals. You really need to do a presure test a visual inspection of the seals is useless in my opinion. Sometimes they only leak when the engine gets hot.
My .02

[quad59]

I had one of these gremilins multiple times throughout and it was never the same thing. I'll list the remedies
replace stator
replace cdi
replaced the coil
exhaust was loose at the jug
and the finally was, it was down on compression.
I have had that problem countless times with something different fixing it everytime.

[selbygirl]

when you cut the kill swithc wire that may have bin your ground wire and i had a problem with my petcock i ran a fuil line from the gas tank to the carb and it cleared up i have notice when its elactricol the plug looks blackish good luck tommy

[Colby@C&DRacing]

You didn't mention if you have a tether kill switch or not but I just had the same issue with a customers DRR 70 it ran good on the bottom but missed on cutout on the top tried everything and found the Prodesign tether was failing. Just a thought :)

[mcwilly]

Originally posted by Colby@C&DRacing
You didn't mention if you have a tether kill switch or not but I just had the same issue with a customers DRR 70 it ran good on the bottom but missed on cutout on the top tried everything and found the Prodesign tether was failing. Just a thought :)

We're running the Prodesign as well.....


You said you checked the crank seals. You really need to do a presure test a visual inspection of the seals is useless in my opinion. Sometimes they only leak when the engine gets hot.

I have no prior experience inspecting/replacing crank seals....I was given the idea to spray behind the flywheel and behind the front variator while motor is idling and warm. The rpm's should raise or kill the motor if a leak was present. The rpm's never fluctuated.

[quad59]

from experience with mine on the stator side that piece of black gasket material will keep the carb cleaner from getting back in there. If it was a crank seal though I would think you would see some signs of a lean condition on the plug.

[jerkyboy]

I just had this problem with cutting out it sounded elecrtical. It would pull hard for 150' and about 200' then start to cutout or somtimes feel like it lays over ( go lean). I kept throwing bigger jets at it till it got better but the plug got darker and darker as I went up in jet sizes. So I decided to presure test the case thats how I found the crank seal leak. Just felt like sharing

[stoneman]

My sons 06 90cc air cooled was cutting out on top end.
It was the tether cord shorting out.:eek2:

[coffing918]

Originally posted by stoneman
My sons 06 90cc air cooled was cutting out on top end.
It was the tether cord shorting out.:eek2:
had the same problem on our 50 stock

[BradLoomis]

Check the slider 1/2 of the variator. If you can rock the variator on the steel sleeve, the bronze bushing is worn out and as the belt raises to the top of the sheeve it puts to much pressure on it to freely slide. It doesn't make the motor miss, but will make it act as if it won't rev pass 1/2 throttle.