My thatsdax engine dies or died on me : /

Dr. Doom

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Nov 14, 2009
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Maple Shade, N.J., 08052
I've had this engine for quite a while and filled the gas tank for I don't know how many times. The problem I have is that recently overnight my bike noticeably lost power and speed on the straight-aways. I recently changed the sprocket from 44T to 36T and understand the concept with the speed change. It was great I went nice and fast but basically after this change this problem occurred! This bike started up for me no problem, I rode around with impressive speed, then I loosened the throttle and it was as if later I couldn’t go that fast anymore as before again. I thought it was a fluke but on my way back home it became so weak I had to start pedaling.

I cleaned the wires, cleaned my original spark plug, messed with the gas on/off, and then later cleaned the air filter. Problem did not fix when I tried to start her up again. All I got was her having the hardest time starting while making these loud unhealthy popping noises occasionally. When it finally started the engine was running only when the clutch was pulled in out of gear. I checked gaskets after that but all looked fine. Does this sound familiar to anyone who may know the answer to an easy fix?
 
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Have you checked fuel flow to the carb (both external and screen filter in tank) remove the screw below the fuel bowl, and watch for flow? Have you checked the compression....I'd start there. Popping noises brings to mind timing. Check the key that holds the magnet in place. How is the fire to the plug?
 
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Go step by step starting by the cheapest
Clean the carb. when the jets gets cloged up the reduce engine performance really bad
Clean exhaust. when they get clogged up they can reduce engine power by over 50%
change spark plug(the chinesse one is junk!) get a NGK or a similar high quality plug(dont forget to gap it propely!)
Get a new high quality plug boot and wire. The chinese one is worser then nothing:whistle:
Buy or make some HIGH quality gaskets because the chinese one can fail and destroy your engine(the carb manifold one especialy because if they blow false air entrance will make your engine run lean and seize up! and also the exhaust one!)
IF THIS list dosent do anything to the engine then ask someone(or me:D) or search in this forum for old threads because they can be very helpful!
Good Luck
G-Superior:D
 
to check for compression just lift your wheel off the floor and try to turn the engine over(with the plug screwed in but the wire off so it will not fire up and injure you!)
If is hard then its got compression(can also be seized if it is really really hard)
another way is to get the plug out and turn the wheel and put your finger in the plug hole, if it sucks the pushes it out then you got some compression
G-Superior
 
No. What kind of tool do you need to check for compression?
Ummmmmm maybe you need to place the engine back in the box and return it....all kidding aside, the compression is checked with a compression guage/tester.

http://www.autozone.com/autozone/ca...r&categoryDisplayName=Tools&_requestid=869985

There are other places that you can get them cheaper. I'd have one around, it's a very important tool for internal combustion (non diesel) engines. If it has a spark plug you need one.

http://shop.ebay.com/i.html?_trkpar...&_sticky=1&_trksid=p3286.c0.m14&_sop=15&_sc=1

http://cgi.ebay.com/ebaymotors/Comp...Z300421364368QQptZMotorsQ5fAutomotiveQ5fTools
 
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to check for compression just lift your wheel off the floor and try to turn the engine over(with the plug screwed in but the wire off so it will not fire up and injure you!)
If is hard then its got compression(can also be seized if it is really really hard)
another way is to get the plug out and turn the wheel and put your finger in the plug hole, if it sucks the pushes it out then you got some compression
G-Superior

Yes SOME compression, but these engines won't run on just some compression. I'd venture to say you need at least 90# minimum. And to tell you the truth, a person not familiar with compression or a tester won't be able to tell if there is enough to begin with. Second, compression at low RPM as spinning the wheel is nothing as having the engine turning over at 2-5 MPH.
 
I can check any engines compression by just turning then over, but I forgot to say that i have quite a few years of experience and lots of engines trou my hands :rolleyes:
you will get better over time:whistle: but a compression tester will help a lot, my costed something like 20$
G-Superior
 
Compression testing should be done at 'normal cranking speed'. On these bikes, that's pedal-starting speed. With a stock (non-slant) head, you're looking at about 95psi, as Ron says.

The real point that I wanted to make, though, is that you say you cleaned the original spark plug.
That implies that you haven't tried a new plug. Do that first. Try an NGK B5HS or B6HS.
 
Check your throttle cable, it may not be opening up you carb slide all the way up,take off air cleaner and turn throttle, is the carb slide going all the way up?
 
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