90cc busting & swallowing reeds. Heeeelp!!

[TeamNeilson]

Hey there.

Ive got a strange issue that everyone is scratching their heads over.
Last weekend out of nowhere my sons 90 died at the finish line with a pop.

We checked all electrical and seemed fine, then we pulled the reed cage and there were no reeds left. Gone inside the motor.

I pulled apart the motor to clean it out, reassembled the motor and put in new carbon fibre reeds. The bike came to life nicely, seemed to rev out great in the backyard, so we took it to the track. We didn't make it to the first turn when the almost electrical sounding stumble could be heard, then a backfire, then it shut off again. Pulled The reed cage and again the motor sucked in apiece of reed.

The funny thing is that the reeds look like they are being blown out into the carb before they break and ultimately go into the motor.

Compression is 150 psi. Main seals did not blow out. Plug color looks good.

I'm sitting at the track right now trying to sort this out .... Has anyone seen this before?? Is it electrical maybe? We did have a short over issue where electrical we going to frame and making the bike untouchable (electric shock) but after pulling everything apart and checking everything that issue seemed to have disappeared

heeeeeeeeellllpp. Thanks in advance

Did you have your tether wire wired backwards? If you had the ground hooked up wrong that was what was shocking you. It has to be electrical and causeing a backfire thats why your loosing your reeds. Make sure you have a GOOD ground. Are you using pvl or stock componets? Ill try to help you all I can,

[TeamNeilson]

Hetrick hi rev cdi, stock coil and stator.

The first time it sucked in reeds there was no issue with shocking. Just did it out of the blue.

During reassembly aftr the second set of reeds I think I mixed up the black wires. But sorted that out and it still sucked in the reeds.

It's all buttoned up to spec and still seems to stumble and mid throttle, backfire and blow out the reeds


Thanks so much for the quick reply, my little guys day is over, but mine is just beginning

i wonder if I should just put fresh coil, cdi, stator and kill switch in but I'm afraid it's just going to do the same. :(
thanks again

[Coley'sdad#8]

yes it is electrical, ignition is what causes the popback or backfire. could have lost your engine to frame ground, I have 2 different grounds wired.

[TeamNeilson]

You guys rock.. The problem, since not too many people have heard of motors popping reeds like they are candy (3 sets of reeds in 90 seconds (combined) of riding)...


I'm not.. I repeat not comfortable with wiring, I wouldn't know one wire from the next if it wasn't 'match this color with the same colored wire on the other side' kind of deal.


So Marc at Hot Quads sent me up, stator, coil, cdi and tore out all the electrical on the bike and started fresh.

I heat shrunk all the connections as well as soldered all wire attachment points, die grind all the frame mounting points, added grounds for the motor and bolted it all together. One kick and it was idling again.


We got 3 SOLID practices out of the bike without even a bobble... Come race day the MOTOR held up like a champ, but sadly the little DRR frame is now 2 drr half frames... she pushed the shock right up into the seat... and now, i'm scrambling for a chassis (and they are not easy to get in my neck of the woods... note.. i'm looking for a good strong rolling chassis)


So thank you very much for your quick replies.. They soothed my nerves and got my 8 year old back out doing something he loves... even if it was just for 10 minutes :)

[thequadfather+2]

Just a guess, does it look like this? Our did the same thing last year and knocked the seat off when it happened. Just take it apart and gussett it

[thequadfather+2]

twisted the frame a little

[thequadfather+2]

started with this.....

[thequadfather+2]

Its been like this almost a year now and probably 40+ races...no more breaks, no problems.

[TeamNeilson]

Looks very much like that, except the metal is torn and twisted, from under the shock mount, it tore through the gusset, along the frame and then out the other side up in front of the main frame support upright. It's a mess and looks pretty gnarly. I'm sure its fixable, but i think that the frame is already pretty weakened. It just keeps breaking in weird places even when I have gussets


I do like what you did and might have my welder copy it.. That big plate you have behind the shock mount, is that just a plate or is that stock? my bike doesn't have one .


Also, it looks like your gusset made a box around the 'battery' area, am I seeing that right?


Did you do the upright bar between the upper shock rail and the rear engine crossbar (the one that the chain likes to chew on) ??


Thanks so much for the pics.. I do want to get it fixed, even if it gets us through a weekend.. one weekend at a time.

[TeamNeilson]

Oh. Can you send me a bigger picture of the completed gussetting? I want to bring that to my welder on Monday ;)

[thequadfather+2]

yes, send me your email address. I had to resize them for the forum. The gusset's are a little over the top compared to what most people do.

The plate was just cut to fit around the shock mount. The shock fits just fine. The plate in front of it does have a section cut out for the battery because at the time we were still running the battery. I went and purchased the smallest motorcycle battery I could find, measured it, cut the hole just a little bigger and welded a strip inside the hole for the battery to sit in.

I didnt put the additional brace in that you are talking about, it probably wouldnt be a bad idea but so far I havent had any problems. Even through jumps like this.......