I just rebuilt my 2001 blaster motor. Purchased the bike and the crank went in a few weeks. Purchased a wiseco top and bottom end kit with a a .60 over piston. Had the cylinder bored out properly. Built the motor properly to my knowledge and specs of the haynes manual. Ran great for 3 hours. Started to backfire. Retightened the head bolts cause of the new gasket. Backfire issue stopped. Now the motor is revving up to full throttle on its own. I rode around for an hour just crusing less than half throttle with no issues and after i do a few 3/4 throttle pass it seems to want to do it. Is this a carb issue
rebuilt motor now over reving on its own.
- Thread starter drty jrzy
- Start date
Was the motor heat cycled and the bolts re tightened before you rode it.
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Were you low on gas when this happend? because something simlair happend to me and its becuase when you have the petcock on the "on" position it sucks up more fuel but since your low on gas/fuel you need to turn the petcock on the "res" position so it can use less gas/fuel so it wont lean rev.....Always check ur gas after riding for about 30-to an hour to see where your at!
I apprecite the quick response time. Im under the assumption that the quad is bone stock with no mods anywhere. The previouse owner was a back yard butcher, Pourly maintained ,stripped heads on nuts and bolts.All head bolts were stripped out. Drilled out and added inserts from msc industries. All parts appear stock. Exhaust ,carb, front pipe etc... the previouse fly wheel was ruined magnets were broken stripped where the puller goes. Had to weld the tool on to get it off. Bought a new/used one. After build i did a compression test got 120 psi. No leak down test performed. Im assuming jetting is stock. After the reving/ backfire incident i took the flywheel cover off checked the woodruf key, that was good and in place. I checked the juts on the head and retightened them to torq specs again(back fire stopped) i pulled the plug it wasnt wet and didnt look in bad shape. Bike starts and idles fine runs great till i go more than 3/4 throttle. Ran motor several times to heat and let cool without riding it and checked bolts for tightness. Reed valve cover was also still tight.
Also when its was at high idle i hit the kill switch and it did nothing. Had to pull the fuel line off.
Sorry to post in short blurps... im sure its annoying. When i pulled the cover off the flywheel i had a little bit of case oil on the cover just a few drops. Can that cause the issue
Sounds like you are suffering pre ignition caused by a lean mixture which is detonating.
Oil in the flywheel cavity sugguests a worn crankshaft seal causing and air leak.
Leak test now before starting the motor again.
A tight reed cover bolt is no indication that the cage is not leaking. Sometimes an over tight bolt will deform the cage and cause leakage.
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Thanks for the info. I will test tomorrow hopefully. I found a site on how to make one from home depot parts. Any thoughts on a brand of carb to get( im not assuming its the issue ) ..... was considering getting new front pipes and a silencer any thoughts on a brand.
On a choice of pipe it all depends on how you ride and where you want the most power, high/mid/low.
Stock carb will work well with minor mods, no need to go bigger with a 200cc motor.
So I finally got the time to pull the motor to do the leak down test. I noticed that the reed valves aren't closed completly when I look into the cage. Could this b causing the over rev issue. Will b doing the leak down test in the morning. Will post my results.
Poorly seating reeds will cause hard starting.
Over rev is usually cause by an air leak or maladjusted idle setting.
Over rev is usually cause by an air leak or maladjusted idle setting.
Finally did the test today. I had the list of all the parts i needed to make the tester and i realized duh i build inground pools and we pressure test lines for leaks. The recommended test psi is similar for both pool pipes and the motor but our tester use a compressor like that of which u would use to fill tires not a viant one. . I tried to upload a picture of our tester but it im not sure how yet. My test revealed a bad seal behind the drive gear on the crank shaft in the fluid case. Also found a leak between the reed cage and the the rubber the carb goes into. Not where the gasket meets the cage and the motor but where the carb boot meets the cage. It looks like the rubber behind it is to compressed to make a tight seal " my main air leak" i believe. It took me a few times of reseating and testing over and over but the motor has been sitting at 7 psi for about 15 minutes now. Im gonna order a new rubber piece that the carb goes into. Also does anyone know of or can suggest aftermarket chain adjusters. All in all i feel not to bad of a job for a first time 2 stroke rebuild. Thank you everyone for your input and further support with my questions.
Take some rep for heeding advice and acting on it.
The carb boot and reed cage are notorious for leaking, especially if the tensioning procedure is not done correctly.
Copper RTV can be a great help in sealing that rubber gasket seal.
You will have to replace the crank seals, but you can do the job without splitting the cases.
The carb boot and reed cage are notorious for leaking, especially if the tensioning procedure is not done correctly.
Copper RTV can be a great help in sealing that rubber gasket seal.
You will have to replace the crank seals, but you can do the job without splitting the cases.
So i put the motor back on had it running at idle for a few minutes everything was good. Started over revving once i got more than half throttle into it. I used black rtv on the rubber seal but perhaps i didnt use enough or its not temp rated high enough. Didnt wanna over do it. Im gonna order a new carb boot and new chain stays as they are all stripped out. If i get the copper rtv should i just gob it on there. I did a thin layer of the black rtv, waited an hour and leak tested with no problems. Im assuming the boot is the issue as it looked to b not flat anymore when i examed it
Take the reed cage and carb boot off and clean the black sealant off.
Then smear a light coat of copper high temp RTV on and re tension to 5.8 ft lb, diagonally and incrementally.
Leave overnight and then leak test again.
Then smear a light coat of copper high temp RTV on and re tension to 5.8 ft lb, diagonally and incrementally.
Leave overnight and then leak test again.
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