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Post by bumtrain on May 30, 2018 22:10:20 GMT -5
Please help. I have installed a big bore kit (50mm) into my 50cc 139qmb engine. I was able to get it started the first time with a few kicks (electric start doesn't work because of crappy wiring). The scooter now runs like crap. I first thought it was because the carb wasn't tuned. before I installed the BBK I put on a 150cc carb. So I would think that the engine would have enough fuel to run right. I began to research lean and rich conditions and it seemed to be Rich. It seemed to be bogging down after getting on it (if this isn't rich please tell me) So I moved my adjustable needle in my carb up rings. This seemed to improve some. I also took it back apart and checked the valve rocker clearance adjusted it to the correct height and noticed my camshaft was not aligned with TDC by one link. After doing all this it started and was still running like crap. Also, It seems that a clicking noise is now occurring, maybe I didn't tighten one of the rockers down tight enough and it came loose, I'm not sure. I am at a loss for what to do next. I've been scrapping the bottom of this forum for info and found some answers but not what I needed. I was hoping I could find some help with making my own post. Thanks for your time.
Let me know if you need more info.
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Post by greginisn on May 30, 2018 22:52:18 GMT -5
Maybe this is just a flying leap for an answer BUT using a 150 cc carb might just a little too much carb. The stock jets are way big as is the 24 mm venturi. Your air fuel mix isn't mixing like it should because of lazy air flow thru the carb. Go back to your 49 cc carb and upjet a bit and your scooter's life will change for the better. Just my 2  anyway. Good luck, Greg |
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Post by bumtrain on May 30, 2018 22:55:43 GMT -5
Maybe this is just a flying leap for an answer BUT using a 150 cc carb might just a little too much carb. The stock jets are way big as is the 24 mm venturi. Your air fuel mix isn't mixing like it should because of lazy air flow thru the carb. Go back to your 49 cc carb and upjet a bit and your scooter's life will change for the better. Just my 2  anyway. Good luck, Greg Hey, I'll try it out. At this moment I'll take any advice haha. thanks for the help |
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Post by diynuke on May 31, 2018 1:42:50 GMT -5
Please help. I have installed a big bore kit (50mm) into my 50cc 139qmb engine. I was able to get it started the first time with a few kicks (electric start doesn't work because of crappy wiring). The scooter now runs like crap. I first thought it was because the carb wasn't tuned. before I installed the BBK I put on a 150cc carb. So I would think that the engine would have enough fuel to run right. I began to research lean and rich conditions and it seemed to be Rich. It seemed to be bogging down after getting on it (if this isn't rich please tell me) So I moved my adjustable needle in my carb up rings. This seemed to improve some. I also took it back apart and checked the valve rocker clearance adjusted it to the correct height and noticed my camshaft was not aligned with TDC by one link. After doing all this it started and was still running like crap. Also, It seems that a clicking noise is now occurring, maybe I didn't tighten one of the rockers down tight enough and it came loose, I'm not sure. I am at a loss for what to do next. I've been scrapping the bottom of this forum for info and found some answers but not what I needed. I was hoping I could find some help with making my own post. Thanks for your time. Let me know if you need more info. However its not the big bore that isn't working xD its you that doesn't know how to properly install a big bore and yeah go back to a 19/18mm carb they are big enough. |
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Post by bumtrain on May 31, 2018 8:43:23 GMT -5
Well, it was the first one. What are some tips or things I should have done to ensure that it was installed correctly? |
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Post by dexameth on May 31, 2018 9:52:26 GMT -5
I run a 24mm carb with a 115 jet on a 52mm stroker build, and did on a regular 50mm build and 108 jet. They run great with that carb setup...
Did you gap/clock the rings correctly?
Can you explain the issues more clearly?
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Post by 90GTVert on May 31, 2018 9:55:02 GMT -5
Hearing the ticking and doubting your work there would make me check over the valves first.
Have you tried any other carb tuning? The bigger carbs can be harder to get good throttle response from.
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Post by GrumpyUnk on May 31, 2018 10:16:04 GMT -5
I agree with the suggestions, based on my experience with other projects. When you make a major change, such as a BBK, you might want to consider doing ONLY that change, from stock, and making that work before adding MORE changes, such as a muy larger carburetor. Fiddling with the jets before you are sure the 'mechanicals' are done properly is just adding more fuel to the 'What Causes The Problem' question.
Make one change, or limited changes, at a time, get that working, and then make more changes, one at a time, would be my suggestion.
Did you have any problem getting the piston & rings to slide into the cylinder when you were assembling? If there was any difficulty, it might be worthwhile to take it apart and check that the rings did not get wrinkled.
Take the blower housing off, and set the flywheel to the "T" mark. Look at the cam sprocket alignment. If the two holes are not even on either side, you need to do some adjusting. If they are, good. It might not hurt to remove and re-install the chain tensioner to be sure it 'released' and is tensioning the chain. You can try to wriggle the cam sprocket to assure yourself it is tight. No wiggle allowed.
tom
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Post by bumtrain on May 31, 2018 11:42:53 GMT -5
By rings do you mean piston rings? I believe those were good when I put the piston in. Hopefully, this explanation is more clear. My scooter now can only go about 20mph now when before I could go 35. I cant hit the higher RMPs and the scooter just doesn't want to go. I am also hearing a clicker or ticking noise that is pretty noticeable. I think its one of the rocker isn't tight enough. These are my issues. I can also post pictures of everything to make it easier to see what I am seeing
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Post by bumtrain on May 31, 2018 11:45:28 GMT -5
Hearing the ticking and doubting your work there would make me check over the valves first. Have you tried any other carb tuning? The bigger carbs can be harder to get good throttle response from. I am going to check the valves and make sure they are correct. I haven't done anything besides changing the needle height. I was waiting for more main jets to come in the mail. |
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Post by bumtrain on May 31, 2018 11:49:12 GMT -5
I agree with the suggestions, based on my experience with other projects. When you make a major change, such as a BBK, you might want to consider doing ONLY that change, from stock, and making that work before adding MORE changes, such as a muy larger carburetor. Fiddling with the jets before you are sure the 'mechanicals' are done properly is just adding more fuel to the 'What Causes The Problem' question. Make one change, or limited changes, at a time, get that working, and then make more changes, one at a time, would be my suggestion. Did you have any problem getting the piston & rings to slide into the cylinder when you were assembling? If there was any difficulty, it might be worthwhile to take it apart and check that the rings did not get wrinkled. Take the blower housing off, and set the flywheel to the "T" mark. Look at the cam sprocket alignment. If the two holes are not even on either side, you need to do some adjusting. If they are, good. It might not hurt to remove and re-install the chain tensioner to be sure it 'released' and is tensioning the chain. You can try to wriggle the cam sprocket to assure yourself it is tight. No wiggle allowed. tom Okay, I will look at all those things. I will check the rings and make sure there is no damage. I will also put back on the old carb and tune from there. I recheck the cam alignment and that was perfect. I will check the chain tensioner. Thanks for all the help everyone I really appreciate it  |
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Post by bumtrain on May 31, 2018 12:56:05 GMT -5
Here is a video of the noise that it's making. I went in and adjusted the valves again, they were a little loose. It is still making this noise after. What could this be?
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Post by dexameth on May 31, 2018 15:16:58 GMT -5
Oh no, sounds like your con-rod bearings are done. 2 locals here had the same noise (almost sounds like variator rattle) and both times turned out to be a bad crank.
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Post by 90GTVert on May 31, 2018 16:09:49 GMT -5
Sure the piston wasn't kissing the crank at BDC?
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Post by bumtrain on May 31, 2018 17:26:39 GMT -5
Sure the piston wasn't kissing the crank at BDC? I don't think it is. I would turn the piston by hand and wouldn't hear anything smack together. |
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anyway.
anyway.
