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Post by E on Sept 28, 2014 19:48:13 GMT -5
So I decided to start working on a Tao Tao engine that I had left from a scoot that I sold a while back. It had bent valves, so I replaced them. I decided to check the rest of the engine since I had half of the top end off. I checked the piston and re aligned the rings, checked timing and adjusted valves. Put her back together, cleaned the carb and capped off the vacuum inlet. Threw in a new plug, checked for spark and did a half assed compression test with my finger. Checked all the connections again, crossed my fingers and tried to start her up. She turns but has no signs of starting. I even tried starting fluid to get something from her. No luck ....... I'm stumped!  ?? Any guidance would be awesome |
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Post by usmcdoc on Sept 29, 2014 18:46:17 GMT -5
Working on a similar issue.. Guy burned his exhaust valve from running with no muffler. Valve and valve seat were shot!! It lapped 2 new valves in the valve seats..tried the head and still compression leak. So I put the same new valves in another head..lapped them well and still no start and low compression. Pulled the head and filled the bowl of the head with gas to check for valve seat leaks..yup the exhaust seat on that one leaked as well. Doing this parts and labor free for a fellow Vet..so I am losing money by spending time and money on this project.. But I will do anything to help others that can't afford parts and labor..especially a fellow Vet. But my brother this is gonna break me. So now I am search of a good used and known to work 50cc stock head. If I figure this problem out and discover anything being overlooked..I will let you know on your post here. Not to brag but I am well versed on repair of these Chinese Scoots (hence why I have a highly spoken of parts/repair business) But even we that have worked on these.. this many years..well..we still run into problems. It's like this.. I have a cousin that has been a NASCAR mechanic for over 24 years and the beginning of race season this year they had an engine that they just could NOT get a good oil pressure on... They tried everything only to find out that the company they were buying Crankshafts from...had a run of bad Cranks where the oil passages were completely open/drilled out. So they kept trying new oil pumps etc..to no avail. So ya see..sometimes it is not the one working on the engine..it is the one who supplies the parts that is in error.  But again..if I come up with anything..I will let ya know. As I said..right now I am looking a for a good used stock 50cc head to buy. I would just buy him a new one..but 1. I am not rich. 2. I already have lots of time and money for parts and labor in this thing... Glenn |
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Post by Deleted on Oct 8, 2014 16:40:17 GMT -5
Working on a similar issue.. Guy burned his exhaust valve from running with no muffler. Valve and valve seat were shot!! It lapped 2 new valves in the valve seats..tried the head and still compression leak. So I put the same new valves in another head..lapped them well and still no start and low compression. Pulled the head and filled the bowl of the head with gas to check for valve seat leaks..yup the exhaust seat on that one leaked as well. Doing this parts and labor free for a fellow Vet..so I am losing money by spending time and money on this project.. But I will do anything to help others that can't afford parts and labor..especially a fellow Vet. But my brother this is gonna break me. So now I am search of a good used and known to work 50cc stock head. If I figure this problem out and discover anything being overlooked..I will let you know on your post here. Not to brag but I am well versed on repair of these Chinese Scoots (hence why I have a highly spoken of parts/repair business) But even we that have worked on these.. this many years..well..we still run into problems. It's like this.. I have a cousin that has been a NASCAR mechanic for over 24 years and the beginning of race season this year they had an engine that they just could NOT get a good oil pressure on... They tried everything only to find out that the company they were buying Crankshafts from...had a run of bad Cranks where the oil passages were completely open/drilled out. So they kept trying new oil pumps etc..to no avail. So ya see..sometimes it is not the one working on the engine..it is the one who supplies the parts that is in error. But again..if I come up with anything..I will let ya know. As I said..right now I am looking a for a good used stock 50cc head to buy. I would just buy him a new one..but 1. I am not rich. 2. I already have lots of time and money for parts and labor in this thing... Glenn i have plenty of stock heads laying around. $15 shipped if you want one. Neither of you have posted a compression reading. |
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Post by Deleted on Oct 10, 2014 20:21:48 GMT -5
and did a half assed compression test with my finger. Checked all the connections again, crossed my fingers and tried to start her up. Any guidance would be awesome Try it again with a compression tester. 150psi is the lowest reading a 139qmb can still start ok at. |
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Post by 90GTVert on Oct 13, 2014 16:30:11 GMT -5
Whenever valves are bent, everything needs to be examined and at least do as Doc described and see if water or gas will flow through the closed valves. Doesn't take much damage at all to screw up a seat so it won't seal. Even it it just leaks a little and runs alright, it can be a big problem. I found that out years ago when I ported a stock head and it ran well until it started shooting flames from the tailpipe when a tiny nick and leak at the seat caused a burned valve.
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