Adjusting your valves on the Linhai clone engine

[rubicontx]

Thanks for the Bone! This is truly a great site with lots of helpful information!

[csivo]

Thanks for the post-
Really helpful with the pictures. I did my first one today at 800 miles it had almost no clearance on the top valve. But, the bottom one never got done because I rounded that darn bottom bolt next to the gas tank. I posted a thread for some help, and as usual got some good advice, I will try next time. I am open to suggestions though. I got everything buttoned up and the scooter runs great, but I'm sure the exhaust valve will need to be done soon. Thanks for taking the time Rubicontx

[yowster]

Nice pictures and illustrations but there is one problem what is the clearance. I like to know the clearance on the gy6 engines because I've seen it on certain scooter company's from 002 to 0010. I know what's right but I'm asking you.

[bluescoot]

i guess its my turn . scooter has been stalling more frequently and has trouble starting in the morning. I have a cypress 250b w/linhai engine with about 2400 mi. i just hope i dont mess it up and it doesnt start raining.

[rubicontx]

Good luck. Let us know it goes.

[bluescoot]

AMAZING!!!! I got it adjusted and it started up right away even though it was on the center stand over night. i put the body back together and took it for a spin, it didnt stall or die when i stopped at a stop sign and it actually took off when i gave it very little throttle. I did have to adjust the idle screw because i had turned it up previously. I gapped the intake (top) valve at 0.004 in and the exhaust (bottom) valve at 0.005 and those gaps worked for me. I have seen many different suggested gaps and it really depends on where you look. My scooter runs much quieter and smoother and performs so much better, so far.


here is a video of how to do this valve adjustment www.jclusa.com/uploads/Media/MP250A%20Valve%20Adjustment.wmv
but i suggest to try 0.004 in intake and 0.005 or 0.006 on exhaust
it also appears easier if its on a lift or a table, however i just laid on the ground a lot.
good luck to all future endeavors.
and thanks to all for info and feedback.

[utahguy77]

I would like to thank rubicontx, and others on this post for helping me. After buying my 2008 roketa mc 250 b a couple of months ago and after 400 miles it started to stall at stoplights. One time it stalled and i almost couldn't get it restarted. I started to look for help and found this sight and this post. After about 2 weeks of talking myself into do it i took the plunge and did it. Took me about 45 minutes to get all the plastic off and about 20 minutes to adjust the valve's, and about 3 hours putting it back to gather. My scoot had more power and stopped die-ing at the stoplights. has worked well for about a week now. But now its starting to die again, It still has lots of power. Its not die-ing all the time mostly when the bike gets shaken or if i go over a speed bump then stop. dose anyone have any suggestions for me. Rub you get a bone from me for sure. as well as others on here for putting in the clearance

[utahguy77]

So since I got no response from anyone. I decided to check my valve's again. the intake was perfect but the exhaust had closed up almost to no clearance so i re adjusted it and made sure the lock nut was tight. Then I took it out for a spin and the hesitation had stopped. also the battery was leaking a little so I replace it and now i hope all is good. I am having some problems with the temp gauge but I will check other posts about that. Anyways thanks again to rubicontx and others on this post for there help and guidance.

[bananazx]

Thanks for sharing. Great instruction!

[Danny]

I sense a bit of confusion amongst some. SO.
For those of you who are curious a few thousands are in fact critical. Allworlds tight gap per Jim is required.
Intake should be .003 inches or .0762mm
Exhaust should be .005 inches or .127mm
I'll tell you why.
The cam that lifts the lifter and depresses the valve is in fact lobe shaped.
This egg shaped lobe is what gives your cam LIFT and DURATION. That is how different cams are measured.
Lift is how high the valve will open off of the valve seat and duration is how long it will stay open for. This allowing fuel and air to enter and or spent gasses to escape.
Too loose or too tight lifter clearances will in effect change the size of your cams lift and duration due to it's egg shape.
Too large a gap, loose, and your valve will have less duration, open later and close sooner. It will also not have as high a lift as normal, thus reducing the amount of air and fuel the piston can suck in or expel.
Too tight and they might not ever fully close when cold since cold metal contracts.
For these reasons, perfectly adjusted valves should result in easier starts, better throttle response, smoother Idle and less throttle to maintain a certain rpm IE HP=MPG.
Sorry to bore you who already know this. Just trying to help those who don't, understand the why's behind doing it.
If it's worth doing it's worth doing right.

[anaharsh]

such a great job. Keep it up and all the best.

[scooterdad154]

Hello

With the help of this post I was able to stop my 2008 MC54-250B from stalling out. Thanks so much!

However, during the setup for TDC, I turned the variator nut repeatedly and could not get the Timing Chain Sprocket mark and the timing mark near the oil fill to both line up to their respective marks simultaneously. I chose to use the timing mark by the oil fill as it was more easily aligned then the timing chain sprocket mark with it's reference mark.

Is this misalignment of marks unusual?

Should I have split the difference between the two?

What if anything should I do about it?

Thanks
Jim

["Big Guy"]

Probably nothing... sometimes you have to turn it 4 or 5 times to get it lined up properly. Did you take out the spark plug? It sounds like you got it right.


-Rich

[trigger]

Scooterdad154,

Another method on SOHC engines is to adjust the a valve when the other valve is fully open. So when you see the cam depress the valve and open it, the other valve will be fully closed and the gap on the closed valve can be set at this time. Then just rotate the crank to open the other valve assuring the opposite valve will be fully closed. No timing marks required, and job is much easier. It is just the mechanics of the engine.

Hope this helps.

Trigger

[ken425ken]

Valve adjustment is exactly what I needed on my Roketa 250. It use to cut off when slowing to 0mph and struggle to reach 70mph. Now, I have quick takeoffs and can reach 70mph much faster. I can slam on brakes to a complete stop and it never dies. I never had any clicking or knocking sounds so I though it was a vacuum problem. I'm so happy I gave the valve adjustment a try. I gapped the intake at .004 and exhaust at .005.

[mrpolymers]

Great post Rubicontx! I used your pictures and adjusted my valves this weekend on a JCL 250A with the Yamaha/Linhai 257cc engine.

I've owned this 2007 JCL 250A for around three months now. More problems than I ever had when I owned my 2004 Honda Burgman 400!!

The dealer I purchased this from had no clue on servicing this machine. They were a Suzuki/Honda dealer and probably did hand stands when I offered my 150 Kymco Super 8 for this and $300! They should have given me $300 for taking this machine off them. Anyway, I finally got the machine running fairly decently until last week..

Out of the blue, the machine would die when I gave it full throttle. Stranded on a major road near my house. Scoot would not start. I had to call my wife from a very nice guy who stopped by to assist. I forgot my cell phone and never planned on this happening. Told the wife to bring some carburetor cleaner. I found out through accident, the scoot would start when I sprayed carb cleaner into the air box. This seemed to get me going for a few minutes. Made it back home. So, I tore all the plastic off and did the valve adjustment per your pictures.

Well, still did not want to start. I noticed when I left the airbox off, the machine would RUN! I assumed there must be an issue of air/gas. I made a filter out of a home furnace filter. The scoot would run fine until I ran the throttle wide opened! Stalled again! Finally today, decided to take off the carb. I read some where that the fuel mixture screw on the bottom of the carb needed to be 2 1/2 turns out from totally closed. Did this, inspected the remaining parts and assembled back on the scoot! Finally! The scoot would run and I could throttle it up without the dreaded stall and no start scenario.

Remember to check the carb with the valves so you do not go thought the crap I did.

I want to thank the fellow Scootdawg posters for there many great instructions.

[mightyninja]

Just wanted to say great article & pic's.
Thanks to this I've just done my valve's (on a YP250 clone) but same principle.
AS it was the first time it took a bit longer than anticipated though!
All good & the engine is now purring.

Too good

[ez4u2say1]

can you not just put a strait screwdriver in sparkm hole and turn to top center like any other engine?

[edfr]

ez4u2say1,
Yes, or a straw or anything for that matter then when it comes up you know the piston is all the way up, then just to make sure check the sprocket holes and see if they are aligned with the top of the head.

Going by the Timeing marks usually is not good because the firing duration area when the Plug Fires is anywhere before and after the "F" mark which is almost an Inch.
Lefty

[jerryw]

There is a video of the whole process here:
www.killermotorsports.com/articles.asp?id=156

You have to scroll down to it. I followed it. The upper valve adjustment is difficult to reach but dropping the rear shocks allows it without removing the gas tank.

[nrvus]

this posting is very helpful and exact. thank you very much for the info.

[robertd]

Could never figure out why engine quit when stopping, adjusted valves exhaust was really tight. sujest ratcheting end wrench to remove lower cover it fits and is easy to get top bolt loose. thanks robert

[tduhon48]

great post but.. like i said .. can rebuild a chevy 350 all day long but these small engines are like a foriegn language to me ... gonna like my brother do it.. so i getting from what ya'll are saying .. my valves need to be ajusted to get my mc54 250b to do the speed the manual says it should do

[tduhon48]

I DID IT.. I did my valves today... i won't say how many times i had to come in and look at your instructions , some things are better left unsaid. i will say the grasss is dying where i keep walking inside and outside .. lol.. i got the intake set at .004 and the exhaust set at .0055 .. the exhaust was hard to for me to get too.. a .005 is a little loose but a 6 will not pass through so i said good enough.. i was told to set the exhaust at either .005 0r .005depending on who i talked too so i figure right between should be good.. Thanks for this great post.. could not of done it without you... here a big bone dog..

[rubicontx]

Thanks, glad it helped.

[terry]

A question about the alignment marks for setting the valves. I can see both alignment marks, the one under the cover and the one behind the plug above the oil filler. No matter what I do, The marks will not be lined up at the same time. I rotated many times and they are always off be the same amount. Is this a problem to worry about? I think I have set the valves correctly. There seems to be a fairly good range where the cam is not trying to open the valves. On old cars we used to set the timing by turning the distributor to advance or retard the timing. How does the ignition timing work on a scooter? Thank you for any help or information.

[texasmike]

Posting here, as my goal is to do the valve adjustment per instructions, but...I am such a noob....is there information around here on fairing removal?

I have taken the front off to do some work, but have not touched the back or middle. One commenter posted he removed both sides at the same time.

Just wanted to check before I start unscrewing things.

Thanks in advance.

[terry]

Nov 1, 2011 10:01:52 GMT -5 texasmike said:

Posting here, as my goal is to do the valve adjustment per instructions, but...I am such a noob....is there information around here on fairing removal?

I have taken the front off to do some work, but have not touched the back or middle. One commenter posted he removed both sides at the same time.

Just wanted to check before I start unscrewing things.

Thanks in advance.

You pretty much have to remove everything except the front! You have to take it off in layers and remove many screws. The rear part of the body will come off as one piece but you have to remove the tail light section and the seat release cable lock. A real pain to work on! The pictures at the first page of this post are great. So, remove the trunk if you have one, the seat, the aluminum foot plates and lower plastic panels on both sides, the small panel below the tail lights, the tail light assembly, left and right rear body, remove battery and plastic that the battery sits in, and the plastic skid plate on the bottom of the scooter. I probably forgot something but you get the picture!

[mmsobyak]

With all the clearance measurement input, it appears the consensus is .004 inch Intake and .006 inch Exhaust (With .003 intake and .005 exhaust being the next preferred) and, this .001 of an inch difference should not be an issue whichever way you go. It also appears that the exhaust valve is the major culprit of problematic issues.

I haven't done this yet so, I do have two, relevant questions, even though they may seem dumb:

1. In the photos, It's hard to see it the valve covers have rubber or metal gaskets or if there are any at all. Are there and what type? I didn't see any mention of replacing them if there are and, what about using gasket sealant? Is it necessary or recommended?

2. The 19mm crank shaft nut... Is that the one to the right of the timing marks in the photo which shows the timing chain sprocket?

I need to get this right and get it right the first time in one day as that's all I get for a day off and the scoot is my only ride to travel the 14 miles to work.

[oldsjet]

The covers use O-ring type gaskets. Re-usable many times over, no sealant required unless youre having leaks, then its best to replace the O-ring.

The nut thats used to spin the engine over is under the cover on the left side. Its actually the variator nut.

On the right hand side, you pull the inspection plug to witness the timing marks along with making sure the cam gear holes are lining up with the head.