Need CR85 Help!!!

[THARNESS]

Hi Guys,

I've been fightin with Ryan's 90 mod for a couple of weeks and I'm needing some help.

He was riding a couple of weeks ago and after about an hour it developed a miss at WOT. I chanded the plug and checked all the electracal connections and away he went. It ran great for about 2 minutes and started again.

We loaded up and went home for the day. The next day I washed it and cleaned the filter. I also took the carb apart and blew out the jets. It ran great until it warmed up( about 4 minutes) then started missing again.

I have since changed the coil,stator, pulse coil, carb,and jetting. We are running a stock cr85 motor and a stock carb. It is a khein 28mm. The main jet was a 125, it is now a 122. after every change it runs good for about 4-5 minutes then begins missing. If he continues riding it will keep missing worse until it gets to the point it will barly pull itself.

This morning I put the original carb back on but with a 122 main. It ran great for about 10 minutes until Ryan came up pertty short on a double and landed really hard then it started missing again. I doubt that the hard hit had anything to do with the miss, but im running out of ideas.

After work today I am planning on running an extra ground wire from the coil and motor to the frame. I will also unhook the kill switch to see it that may be it.

What am I missing guys? Any help would be greatly appreciated.

Thanks

[mini racer #39]

it sounds like the cdi to me we had the same thing happen ran good cold but after it warmed up it missed, popped, sputtered the cdi boxes warm up also check that maybe it will help

[jerkyboy]

You tried going leaner on the main jet try going bigger.
Is this a new build or somthing you ran last season? Sounds like
when it gets good and hot it starts to procces the fuel differently.
Just a thought.

[THARNESS]

This is a quad that we built last summer. It has been raced in temps from 40-95 degrees without ever needing to rejet. The plug also looks great, but at this point I'm willing to try about anything.

The CDI is one of the few things I haven't tried. I will get one and see.

[wvspeedfreak]

The CDI could very possibly be the culprit.If that doesn't do it,check the fuel tank for something possibly blocking fuel flow at times.Just a thought.

[BradLoomis]

Sounds like a grounding issue. Make sure sure you have good connections and wires between frame, motor and coil.

[dericsdad]

We had the same problem with our bike last summer. Different bike, but same carb. as you.

Check/replace the needle jet in your carb. it gets worn out/enlarged from the needle valve vibrating inside of it.

That could be why you are suddenly chasing your jetting as well.

Check out this link, it is part# 34 in the diagram. It comes out the bottom of the carb, after you remove the needle jet holder. (the part that your main jet screws into).

http://www.keihin-us.com/am/_media/pdf/pwk_parts.pdf

[Nick's #1 Fan]

I'm glad you brought up this question. We had the same issue this weekend down in Southern CA. I just rebuilt the motor from Top to bottom and the bike ran great for a practice then when it started to reach temperature it started cutting out and sounded like an electrical problem. I couldn't narrow it down. I thought it might be jetting and I ended up changing jetting from a 128 to a 140 incrimentally with no changes.

We decided to change out the motor and I used the same carb and the back up motor ran fine.

I was thinking it was the stator but the CDI makes sense.

Please let me know what you come up since it sounds like we are having the same issues.

Thanks

[yfz450bb07]

I had this same problem with Tay's bike and it was the cdi. Changed it out and it ran great again. Also on another note back in the day I had the same problem with my 250R and it was the stator. As soon as the stator got hot it would start missing. Good luck.

[Rcarroll]

Same thing happen to us twice once was the cdi the other time was a broken spark plug wire at the coil
Let us know what fixed it

[90cc DAD]

We had our JB mod out today and the bike ran great for 10 min. and would not pull the face of the jumps. We changed the CDI box and it runs great!!
I got lucky and tried the CDI first!!
This is the second time it has happen. So I would def. change the cdi box and see if that fixes it!!
Please let me know how it works??

[THARNESS]

I ordered a cdi today. It will be a couple of days before it comes in. I'll let you guys know how it goes. Thanks for the help.

[LT80]

The extra ground from motor to frame didn't work?
That sure has fixxed alot of machines.

I agree that it sounds electrical.

[THARNESS]

I ran one continus wire from the coil to the motor then to the frame. I also unhooked the kill switch. Same result. I'm crossing my fingers that the cdi will fix it.

[THARNESS]

Cdi came in yesterday. I installed it but the weather is 33 and raining for the last couple of days. Not going to get dry and warm until next week.

Neither Ryan or myself could wait till next week to see if it was fixed or not. Ryan put on his warmest hunting gear and took off.
Rode it hard for 25 minutes until dark. The neighbors think we are crazy and Ryan propably has some frost bite. But he's young, he'll recover quick.

The good news is the mod ran great for 25mins in the sloppy wet muddy conditions. Never sputtered once. I think it's fixed.

Pell City here we come.

Thanks everyone for all of your input.

[90cc DAD]

Glad to see you got it fixed!!
It was the same thing with our JB Mod.
We changed the cdi box and it ran great!!

[GILCO]

Colby's 105 did the same thing at lorettas in the super mini class cost us a race, changed the cdi when I got home and runs great now. It would be a good idea for everyone to keep a new spare around. Sooner or later it will happen.