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Post by glassvial on Oct 12, 2008 23:32:11 GMT -5
Dang, what a difference....... not only does she purr like a kittie once again without stallin...she is all waxed up and shinning like never before. I cleaned everything from the frame, inside the variator, air cleaner & ect...Not to mention after checking this out adj. valves was a sinch...Also I actually pulled the two back panels off as one..The only tricky part wqas the seat latch...But it was easier than dealin with the screws around the tail lights..That did make a difference. Thanx once again rubicontx....Also thanx glassvial for the #'s Nice  And no problem, there's been times I've had to come back and reference my own posts because I forgot something, great to have that as reference  |
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Post by cptk on Oct 14, 2008 13:37:07 GMT -5
oopsy...Well she was runnin. I obviously did somethin wrong. She ran excellent downhill to work for 25miles. not even a glitch. But 9hrs. later she fired right up and with a load at around 2-4 thousand rpm she puttered & died. The little flower was not happy gettin a call at 11:45p.m. to pick me up...so heres the deal....I believe I just need to readjust valaes, but while I was tinkerin I moved fuel mixture screw out to 2&3/4 turns, also removed canister capping line from air filter, gas tank, and made one hose from some doohikie( egr valve ) to intake. So maybe I should have done one at a time....But ya get to tinkerin & it just gets goin.
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Post by monkeywrench on Oct 16, 2008 13:00:59 GMT -5
Another happy customer, rubicontx!
Like most, at 2500 miles, intake valve OK, exhaust no clearance.
Cold naturedeness is GONE, power is BACK BETTER THAN NEW!
With your procedure in hand, it was just like knowing what I was doing!
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Post by orgnyst on Oct 19, 2008 7:05:59 GMT -5
;D I'm new the scooter world and soon after buying my machoman 260 scooter mc-54-250b that damn thing starting stalling out when stopping at traffic lights, etc. Found this post - Thank God for Google and Internet - followed the steps and problem solved. Your instructions were perfect - ONE question?? The sound of the engine is a little different now - before there was absolutely no play/clearance between the rocker arm and valve - I adjusted to .0017 and I can hear valve tapping - Is this normal or have I left too much gap? Should I be hearing this?
Beside this change - I runs GREAT - seems more responsive, starts a lot more quickly than it ever did and no longer stalls out.
BTW - this started happening around 400 miles
Thanks for the GREAT post and details
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Post by orgnyst on Oct 19, 2008 7:12:03 GMT -5
Also noteworthy - My fiancee and I purchased this scooter from www.scooternitro.com although we did not have a bad experience buying from them - it appears they have gone out of business - thus, the end of our so called 36 month warranty. Does anyone have a recommendation for buying supplies, parts online. Also, if there is anyone in South Florida, I would also like to find a reputable mechanic when the day comes to completely overhaul the engine. Thanks |
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Post by harrywr2 on Oct 19, 2008 8:50:44 GMT -5
I adjusted to .0017 and I can hear valve tapping - Is this normal or have I left too much gap? Should I be hearing this? Old school valve adjustment, before the widespread introduction of Hydraulic Lifters in cages. Tic,tic,tic is good, tap,tap,tap is okay(we used to call them tappets), rap,rap,rap is too loose. Silent was either 'perfect' or too tight...impossible to tell since there was no sound. |
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Post by earlwb on Oct 19, 2008 9:01:16 GMT -5
The valve gaps are supposed to be .004" inches intake and .005" inches on the exhaust. 0.0017 is too small.
Yes the valves will tic a little. That is perfectly normal.
On a hot summer day the racket that comes off my Harley's internal parts clicking, clacking, etc. is almost deafening.
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Post by orgnyst on Oct 19, 2008 11:43:01 GMT -5
Thanks a Million - they sound like tic tic tic - so, I guess things are pretty normal.
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Post by cptk on Oct 19, 2008 18:56:54 GMT -5
well folks to finish my saga... I readjusted valves ( not really just checked & all was good) ,re-installed canister and reset carb to 2-1/2, also replaced vacume lines with higher quality hose and so far all is good . took it for a twenty mile cruiz after and she handeled like a champ. I got to admit though me and my nieghbor cant figure out why adjusting valves would make a difference in the stalling issue. But it sure did & that is for sure....Thanx all...........
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mackm
Junior Dawg
Posts: 5
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Post by mackm on Oct 23, 2008 12:48:15 GMT -5
My Linhai 250CC manual said to adjust cold Intake valve to 0.08mm - 0.10mm and the Exhaust to 0.16mm - 0.20mm? Please let me know why your adjusting your valve gaps to be .004" inches intake and .005" inches on the exhaust. Also do you know what the compression is on the Linhai Clone engines after adjustment, my compression is 145psi?
Thanks!
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Post by A.B.Normal on Oct 23, 2008 18:24:28 GMT -5
Throwing you a bone for one of the best posts on repair and maintenance!
Well done!
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Post by oldnslow on Nov 3, 2008 13:45:08 GMT -5
 Like MackM the specs that I have for my Linhai/Yamaha type engine are: intake valve 0.08mm - 0.10mm, exhaust valve 0.16mm - 0.20mm. This puts my exhaust valve gap at .007 not .005 as EarlWB posted or .004 - .006 as Glasvial posted Why are there such differences for the exhaust gap? 
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Post by jim63 on Nov 3, 2008 15:11:14 GMT -5
I am not a small motor mechanic, but .001 is not a whole lot difference. I actually adjusted both intake and exhaust to .006. Was the smallest I had in my gap gauge set, didnt think it was necessay to buy a new set for .001-.002 difference. My scooter since the valve gap adjustment runs good with no ill effects so far. I figure if I was to error on gap, better alittle on the high side than to tight.
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Post by earlwb on Nov 3, 2008 16:32:19 GMT -5
I think you are correct in that the valve gap is supposed to be 0.08mm intake and 0.16mm exhaust. I am probably getting senile.
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Post by oldnslow on Nov 3, 2008 21:06:23 GMT -5
Earl, can I call you Earl? Earl, most of us on this board wish they were as senile as you! ;D You da man!  |
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Post by unclejay on Nov 6, 2008 17:39:51 GMT -5
You can skip the whole timing chain and timing marks thing by doing it the Army way -
Remove spark plug
Put a plastic or metal rod into spark plug hole
Turn engine until TDC which is when the rod is fully pushed out of the spark plug hole
Are both valves on the seats ? No - rotate engine one more rev and try again.
Really all you want is TDC with both valves relaxed.
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Post by fairtaxted on Nov 29, 2008 22:02:10 GMT -5
I HAD a Roketa MC-54-250b issue that was resolved with the instructions here, thank you. Check out my Youtube video prior to the fix. I show how it stalls. Hope this helps someone!!! www.youtube.com/watch?v=3yknkYm26agCool video, why not make a video showing how to do the valve adjustment while you're at it, I'm sure that would help everyone in addition to the pics. I am currently making another video as I take a moment's break. I have all of body off at the moment and about to get dirty. Will get back to you all soon. Thanks for asking. BTW: Over 3000 miles now, or another 1250 or so since last valve adjustment and is still running top notch. Just verfying valves and then will give oil and lub change, etc. |
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Post by mrcleanisin on Dec 2, 2008 17:44:21 GMT -5
Adjusting the valves to apx .oo4 intake and .oo5 exhaust is probably close enough, but please someone explain why it's so important to line up the timing marks for setting the valve clearance? When you turn the engine and the rocker arms come up as high as possible and you place the gage in the gap is it going to be different if the timing marks aren't exactly lined up? In fact on old car engines I used to adjust the valves with the engine running. Maybe lining up the marks are for ............
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Post by harrywr2 on Dec 2, 2008 18:10:49 GMT -5
Adjusting the valves to apx .oo4 intake and .oo5 exhaust is probably close enough, but please someone explain why it's so important to line up the timing marks for setting the valve clearance? When you turn the engine and the rocker arms come up as high as possible and you place the gage in the gap is it going to be different if the timing marks aren't exactly lined up? In fact on old car engines I used to adjust the valves with the engine running. Maybe lining up the marks are for ............ The highest point actually is correct. Few people can visibly discern a couple of thousands of an inch(I know I can't). Hence, lining up the timing marks..when the timing marks are lined up then one is at the 'highest possible point'. |
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Post by mrcleanisin on Dec 2, 2008 18:41:18 GMT -5
I assume TDC is so one can set both valves at the same time, but if the camshaft is round except for the lope area wouldn't the valves highest point be the same except for the lope? What I'm saying is you could set intake on one stroke and exhaust on the other stroke, or am I wrong on this. Otherwise setting valves while a motor is runing is somehow different???
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Post by mrcleanisin on Dec 2, 2008 19:32:25 GMT -5
My Linhai 250CC manual said to adjust cold Intake valve to 0.08mm - 0.10mm and the Exhaust to 0.16mm - 0.20mm? Please let me know why your adjusting your valve gaps to be .004" inches intake and .005" inches on the exhaust. Also do you know what the compression is on the Linhai Clone engines after adjustment, my compression is 145psi? Thanks! Where can I get a manual for mc 54 250B, which I assume is the same as "My Linhai 250CC manual." Need to know other things besides valve adj. For example, how many turns on the idle screw on the bottom of the carb. Can all the vacuum hoses except the one to the fuel pump be disconnected to give more vacuum to the fuel pump. |
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Post by robcarb on Dec 6, 2008 23:57:08 GMT -5
Hate to pee on your parade, but compared to the honda clone, this process is to hard, for no noticible improvement on acceleration or performance. Viva la 250cc.
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Post by harrywr2 on Dec 7, 2008 12:05:52 GMT -5
Hate to pee on your parade, but compared to the honda clone, this process is to hard, for no noticible improvement on acceleration or performance. Viva la 250cc. It is not a performance 'enhancement' procedure. It is a maintenance procedure required for pretty much an vehicle that doesn't have hydraulic lifters. If your valve gaps get far enough out of spec a bike won't run all at. If your bike is starting fine, not stalling, no noticeable degradation in performance then the valve gaps are probably pretty close to spec. If your bike is stalling a lot, hard to start then the odds that the valve gaps are out of spec are pretty high. |
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Post by scooterran on Dec 7, 2008 19:15:45 GMT -5
Could this be why I'm loosing power going up hill? I need a valve job?
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Post by harrywr2 on Dec 7, 2008 19:47:26 GMT -5
Could this be why I'm loosing power going up hill? I need a valve job? Unexplained loss of performance is frequently valve 'gap' out of adjustment. It's not actually a 'valve job' as a car mechanic would know it. Which would involve removing the cylinder head. In a valve gap adjustment the only thing that gets removed is either the valve cover or an access panel depending on engine.(And of course plastic so you can get to the valve cover or access panel) Generally there is some kind of mechanism to adjust the 'expansion gap' between the valves and the rocker arms. Without an expansion gap the valves won't close completely when they are hot, or if the gap is too wide, they won't open completely. |
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Post by earlwb on Dec 8, 2008 6:48:09 GMT -5
scooterran, check the valve gaps ion your engine, adjust the gap if needed.
Loosing power going up a hill. How faster were you trying to go? That to me sounds like a fuel issue with the vacuum operated fuel pump. You may need to check the intake manifold and vacuum hoses for leaks, and consider getting a new fuel pump or going for a electric fuel pump instead.
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Post by oldhippie on Jan 17, 2009 21:32:55 GMT -5
rubicontx, thought I'd throw in my two cents worth toward adjusting the valves. I read where a lot of folks are having a problem getting their wrenches in the tight space to adjust the exhaust (bottom) valve. I have found that by using the 8mm ratcheting box end wrench, it is a breeze because it takes up so little space, and because it has the ratcheting mechanism on it. Also, have used the regular 8mm box-end wrench as well and it works good too. And since not many of us have one of the fancy valve adjusting tools, we have to use either a crescent wrench or something else that is handy and just never seems to fit the little square adjuster. Therefore, as necessity is the Mom of invention, I took my Dremmel tool and an odd piece of metal I had lying around, and ground some slots in it that fit the adjusting stem real snuggy. Although it looks really, really crude, it works! One could probably improve on the shape of the tool so it would be easier to use in the confined area, but I guess what I have will do until I can come up with something better. Going to attempt to attach a photo of the tools, but if it does not make the trip, I will try again, however, with my description of the tool, I imagine one could understand enough to make one themselves. oldhippie  |
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Post by allworld on Apr 17, 2009 15:29:37 GMT -5
Valve gaps:
Per Jim at Sunright Int.
For the Linhia 300 (275cc)
Intake should be .003 inches or .0762mm
Exhaust should be .005 inches or .127mm
I only post this as there seemed to be some confusion in the units inches or mm
I also can not say for sure if these values are the same for the 257cc engine or any copies.
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Post by bluesmoke on May 8, 2009 14:29:56 GMT -5
THANK YOU - THANK YOU - THANK YOU
A friend asked me tune up his MC-54-250B for him. He and I have riden together a few times and knew that I was good with a wrench. He kept telling me it would not idle. So I did some internet research and found this forum and information on idle problems and valve adjustments.
I found that both the intake and exhaust were tight almost to the point of no clearences. Adjustinment was a whole lot easier and faster that removing all the covers and side pods. I was pleased to find that the plug had a nice tan color considering the way the engine was previously running. I buttoned up all the engine covers, set the battery cover on, hooked up the battery and it damn near fired right up! I did let it warm up until the fan came on and now have it idling at 1500 rpm. A ran it up to speed and did a hard braking, and it came right back to idle.
I need to check the forum out a bit more to read about the electric choke, and recommended engine oils. I think it best to change the oil after finding the valves the way they were.
Thanks Rubicontx and everyone on here.
FYI - I am restoring a '79 Vespa P200E, as well as a '61 Triumph TR-4.
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Post by dutchscot on May 31, 2009 0:46:52 GMT -5
Thanks Rubicontx...................
I just finished adjusting the valves on my Roketa MC54-250B last night. Previously, I was having starting problems and read a number of threads in this forum regarding starting and stalling problems and valve adjustment as a fix. According to the maintenance schedule in the owners manual, an adjustment should be performed after 1000 miles. So, I took the plunge.
Well, I am happy to report that the scoot is running great this morning and the starting problems have disappeared. Seems like the scoot has more power. I adjusted the intake at .004 and the exhaust at .006. The valve adjustment was the easy part. Putting the scoot back together was the big hassle and the most time consuming. I couldn't have done it without the help of this forum though. Awesome forum and information.
A bone to you!
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Like MackM the specs that I have for my Linhai/Yamaha type engine are: intake valve 0.08mm - 0.10mm, exhaust valve 0.16mm - 0.20mm. This puts my exhaust valve gap at .007 not .005 as EarlWB posted or .004 - .006 as Glasvial posted Why are there such differences for the exhaust gap? 
Broken odometer = No maintenance!
