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Post by Bluefront on Jun 1, 2011 9:42:07 GMT -5
Bad luck for me and my Xingyue 150. The scooter was running good the day before with no symptoms. When I tried to start-up the next morning.......no compression. The starter spun the engine much faster than normal (sounded different). And using the kick starter confirmed the engine had no compression. There aren't many things that can do this.....simply by sitting overnight, after the engine was running good when last turned off. But I've seen it before on some Ford and Nissan engines. I remember it happening on a few Hondas when I was a cycle mechanic. What happens.....the last time you turned off the engine, the engine stopped with one of the valves completely open. The valve seat had become a little loose in the head, and fell out of it's machined hole as the engine was cooling off. The next time you tried to start the engine, the seat became cocked in the hole, holding the valve open......no compression.  If you're lucky, when you crank the engine, nothing hits the piston. The only thing that gets hurt.......the valve, and the valve seat, but maybe a valve guide also. That's what happened to this head.....with 10.7K on the odometer. I'm going to replace the head and valves.......this is a 150cc GY6B engine, and it's different from a standard 150 GY6. I found a new head with valves installed online for $100. If anybody has seen one any cheaper.....let me know. Lucky for me this happened in my garage. But I've never heard of it happening when you were driving along.....when it happens it's after the engine has been sitting for a while. Under racing conditions it's possible....anything's possible then though. Bad luck for sure.  Oh....Scrappy sells a 4-valve head assembly that supposedly will fit this engine. But I'm really only interested in a 2-valve head. Apparently any head for this GY6B engine is hard to find. BMS has one for $125, but I don't know if it comes with valves....I'll find out. Forgot to mention.....the final proof in this matter. When I took off the valve cover, the intake valve had about a 1/4" of free play. That indicated for sure something happened that was holding the valve open. After I saw that I knew the head would have to come off..... |
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Post by Bluefront on Jun 1, 2011 19:00:10 GMT -5
Well BMS answered me back already.....they don't sell the head with a set of installed valves, You have to buy all the parts separately.....nope.
I'm still waiting for a reply from Scrappy......it's off to EBay for the thing unless I hear about something else.
Anybody have info about this thing?
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Post by tortoise on Jun 1, 2011 19:20:39 GMT -5
this is a 150cc GY6B engine Potential resource. |
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Post by Bluefront on Jun 1, 2011 19:27:28 GMT -5
Thanks......that's the only one I've found so far.
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Post by Bluefront on Jun 2, 2011 7:54:04 GMT -5
I found what looks to be a slightly better deal on the head assy, along with the gaskets and studs...... From this Ebay seller. $70 +cheap shipping. I sent a question to the guy. Getting closer here.....  |
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Post by Bluefront on Jun 2, 2011 11:40:47 GMT -5
Update.....Scrappy just contacted me. He doesn't carry one, not yet anyway. Too bad. His prices are usually the lowest around. Strange.....all the 16" wheel scoots that use an air-cooled engine, use this exact GY6B head. You'd think the thing wouldn't be so hard to find. Everybody sells a standard GY6 head..... FWIW......even the valves are different in this head. They have a longer stem. Update....everything is on order. My fingers are crossed that I get all the correct parts. |
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Post by Bluefront on Jun 6, 2011 13:13:15 GMT -5
Learn something new every day.....all GY6B heads are not created equal. Now I knew this new head didn't have a PAIR port (just as well), but I never considered the exhaust port. The site didn't show a picture of the exhaust port. Everything else seems to be the same, but the angle of the exhaust studs is different.  If I grind down a few fins on the head (the arrows), and make some new slots in the pipe flange, I think I can get it to fit. Still considering my options.......  |
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Post by mainepeace on Jun 6, 2011 20:50:41 GMT -5
That sucks.
Simplest thing is to cut/reweld the flange on the exhaust pipe.
Greg
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Post by Premier Scooters on Jun 6, 2011 22:14:19 GMT -5
I'm with maine, that's what I would do.
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Post by Bluefront on Jun 7, 2011 0:54:49 GMT -5
Too bad I don't own any welding equipment.....plus my welding skills are very rusty. I'd probably do it that way. But I'd still need to grind on the head fins to get the flange to sit flat. And the flange has enough material that if I make "U" cuts on the edges, and use bigger/heavy washers, the stock long cap nuts should hold. This scoot has three heavy bolts holding up the single-piece exhaust system. The flange on the head-pipe, and the two studs on the head, play no part in holding the complete system.....they simply seal the flange against the head. This new head is such a good deal I'm not sending it back.....even though the guy said I could for a refund. I'll start the grinding tomorrow early before it reaches 90+ in the garage again. Ah the joys of a GY6B engine....... Let me add this.....it would be extremely difficult to cut off and re-weld the head-pipe flange so that everything would line up perfectly. There is no play whatever in the entire exhaust system.....so all the flat mounting surfaces need to be perfectly aligned, and that includes the flange. If it was re-welded off even slightly, I'd have an exhaust leak at the flange for sure...... |
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Post by Bluefront on Jun 8, 2011 11:22:09 GMT -5
I'm further along now.....it's been too hot here to work in the garage more than a few hours in the morning. Here's the modified flange,,,  Here's what the modified flange looks like held against the new head...  Here's the modified heavy washers that will be used....  To get the new setup to fit through the hole in the shroud, a few cuts were necessary.  And I made an aluminum plate to close off the PAIR hole from the old head... (to prevent air leaks)  I figure I saved about $40-$50 using this particular head over the next cheapest. Even so....I'm not sure the other GY6B heads would have the correct exhaust stud angles. The head from BMS would have cost close to $175 complete with valves , etc. It should have been a bolt-on installation though, without the extra hassle. A few more days to go...... |
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Post by mainepeace on Jun 8, 2011 22:24:29 GMT -5
Looks good! Now hope it doesn't leak!
It's cool about the plate for the PAIR cover. I noticed that the new Peace Sports scoots I'm getting have a similar plate... and this plate isn't just the oval that most people make... this plate is like a spacer that goes under the valve cover and is held on by the shroud.
Greg
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Post by Bluefront on Jun 9, 2011 1:34:00 GMT -5
Couple of things here......this new head does not have the PAIR emission port cast into it (you can see this in the photo of the two heads side-by-side). I've been running with that port by-passed with a metal plate.....identical to the plate offered by many places for the same purpose. This new aluminum plate simply blocks off the hole in the shroud that would have covered the PAIR section of the casting..... Also.....this complete exhaust system is different from other systems I've seen. When you attach the three 10mm bolts that hold the main muffler, the head flange on the pipe is lined up perfectly against the exhaust port, and even without the two cap nuts in place, it still a tight fit against the head. This is the reason I think this new flange setup will hold ok....without any exhaust leaks. I sure hope anyway.....I'll find out soon enough. |
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Post by mainepeace on Jun 10, 2011 0:13:58 GMT -5
I'm sure it will be tight now... just worried about 1000 miles later... but, who knows, your ingenuity might work for the better!
Greg
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Post by Bluefront on Jun 10, 2011 4:20:58 GMT -5
Plan "B".......those little washer extensions could be welded on the header flange, making the flange connection/strength as good as stock. Should I have any problems with this plan "A", that'll be the next step.
The engine is back together now (not started yet). This morning I install the exhaust, the shrouds, and get started on the other nuts and bolts. ;D
Later....Everything except the seat is back together.....cranked the engine over a while without starting. Then adjusted the valves. The valve cover is sealed on good now with hi-temp silicone. It'll have to dry overnight. I'll start it up tomorrow....
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Post by Bluefront on Jun 11, 2011 9:24:13 GMT -5
Success......had it running in my driveway for an hour or so, using my usual procedure after engine work. I run the thing for an hour or so, at an idle, blipping the throttle, occasionally holding it a 3K for a short time, with a fan on it to keep the heat at the normal range. I put something under the engine, to catch any possible oil leaks.  Obviously check for any oil leaks, and any exhaust leaks in this case. Everything seems ok so far. Didn't even need to adjust the idle speed. I did the entire job for less than $100....that included the new head installed with valves, springs, keepers and new valve seals. The head did come with new exhaust studs which were way too long.....I used the old studs. I did buy an extra complete gasket set, which contained a new intake gasket, and a new tensioner gasket. What I didn't do.....remove the cylinder. The cylinder remained tightly stuck to the block, so renewing the base gasket was not necessary. The only plastic that was removed.....the seat bucket, and the battery cover (which exposes the valve cover). I suspect on a nice cool week-end, a person could have done this entire job in one day, less time if you've ever done this procedure before. Taking this to a dealer for the same job......would have been very expensive. I hate to think how much..... Anyway.....questions answered about this procedure here. ;D Oh....this particular failure seems to be very unusual on a GY6. Never heard of it happening before. |
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Post by Bluefront on Jun 12, 2011 5:31:27 GMT -5
Put about 40 easy miles on the new head setup yesterday.....apparently everything is back to normal. Time will tell the whole story, but it's running well so far. For any of you who may want to do a similar job on your 150cc GY6.....it's no more difficult than installing a BBK on a 50cc. In fact you could use the same set of directions. The only major difference is setting the tension on the cam chain tensioner when you reinstall it.....you have to back off the tension with a screw-driver, and while holding the screwdriver, tighten down the two bolts. After everything is tight, you then release screwdriver tension....and the cam chain tension is adjusted automatically. The only special tool used on this job......a 3/8" small torque wrench to set the four nuts that hold the head on, back to specs. Now if I had bought this head without the valves installed, it would have required more special tools and more work. Anybody with minimum mechanical ability should be able to handle this job fairly easily..... |
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Post by Bluefront on Jun 23, 2011 5:45:37 GMT -5
Update......with about 300 miles on the new head, I rechecked the valve clearances. Didn't change any at all. That's a good sign, pertaining to the metal of this new head assembly. No other problems have occurred after this upper-end repair. Passed 11K on the odometer yesterday....... ;D
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Post by dyoung1167 on Jun 28, 2011 12:20:01 GMT -5
i like the way you work, very well done!!!
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Post by chasemon42 on Jun 28, 2011 21:17:35 GMT -5
hi bluefront I have heard people refer to there engines as a B code. I have a motor that ran outa oil while driving/ posted in the 125 cc section and the engine code reads BN157QMJ. I have 13" wheels. I am just wanting to make sure we have the same engine style. Interested in rebuilding mine and your thread will make doing so easier. thanks. just wanna be as close to positive b4 I run off ordering parts.
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Post by Bluefront on Jun 29, 2011 4:54:25 GMT -5
Tell you what....being positive about anything on these Chinese engines, is difficult. I doubt anybody knows the whole story. 125cc/13" wheels? The GY6B engine in an air-cooled 150cc scoot with 16" wheels and a rear disk brake on the left side......that's what I have. As to rebuilding the engine you have.....man what a job. You ran out of oil? Anything in the engine could be damaged, and even if you had all the parts on a bench, it would still be guesswork telling if anything could be reused. I talked to a dealer the other day about a scoot he had just repaired.....the guy drained the oil, then forgot to put new oil back in. It locked up within 3 miles. That dealer (not of the brand scooter that was damaged) searched for several months, but could never find a new engine that was reasonably priced. So they decided to rebuild the damaged engine(a GY6B).....finding all the separate pieces took four months. And the final bill ended up higher than a new engine installed would have been. Plus.....the owner could have bought a whole new scoot for not much more. Identifying a GY6B engine is relatively easy.....the valve cover usually/always has two bolts, rather than four. Remove the valve cover and measure the distance between the head studs.....it's about 57MM on a GY6B head.....the spacing on a standard 150cc GY6 head is about 53mm. If you remove the engine air shrouds...the fins are angled (see the picture below) on a GY6B. The thickness of the GY6B head is about 3".......the thickness of a normal GY6 head is about 2 1/2". Buying a whole new engine? The length of the thing is critical, as is that drum/disk brake thing, as well as the separate housing of the 16" wheel scoots. You've got a real bear of a job there....getting that scoot back on the road. Angled cylinder fins on a GY6B 150cc engine.....  |
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Post by scooter757 on Jul 13, 2011 21:12:54 GMT -5
Hi Bluefront, I bought a 2008 ITA 150 three weeks ago, and the exact same thing just happened to me.... ran fine, started it sunday morning, no compression. took off the valve cover, and 1/4" gap on the intake valve. after reading your post, it looks like i will be replacing the head. would you recommend the one you got on ebay? You mention the perfect fit head from BMS, but a quick google search doesnt pull anything up. Who/where is BMS?
Thanks!
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Post by Premier Scooters on Jul 13, 2011 21:39:34 GMT -5
It's funny the same thing happened to me, I ordered a head and the exhaust stud holes were the wrong angle. I just cut the weld at the flange on the header, bolted the flange to the head, bolted the muffler and header to the motor, tack welded the the header to the flange in the proper position, took it apart, finished welding it and then sprayed it with some black header paint. It worked fine, but you need a welder.  |
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Post by greg on Jul 7, 2012 14:47:14 GMT -5
a welder or a friend that does,or work. or anywhere if you chat with them should be a 10$ job.
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Post by Scooter Boy on Jul 12, 2012 23:01:40 GMT -5
Good Job! Bluefront
For everyone else.
Welding it back is the best way to fix the problem.
If you can't weld it you can also cut the header pipe and use a piece of metal flex pipe & clamps to reconnect it.
Dropping a valve seat does happen. I replaced two 150cc heads a couple of weeks ago and the exhaust seat was loose on both, one had a cracked seat. Two customers in one week, I think the high temps we were having caused over heating of the engines and caused the failure. Both said they ran fine when parked but wouldn't start the next day.
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