|
Post by Enviromoto on Dec 7, 2008 13:34:01 GMT -5
the forum has moved itistheride.boards.net/index.cgiValve adjustment on a 139QMB 50cc 4 stroke scooter motor. You will need access to the engine bay. For me the easiest way to do this is to remove the seat bucket. But everyone has their own way and there is many different configurations of scooters. What your looking to do first is to have access to the top of the motor. After you get the valve cover removed with 8mm socket or wrench you will need to follow these steps. Step 1. Set the engine to Top Dead Center (TDC) On your flywheel you will see some marks. Make sure the T on the flywheel lines up with the the timing tab. Also check your camshaft and make sure your timing marks on line up with the top of the head. Make sure that you are setting the engine at TDC on compression stroke. The T that lines up with the timing tab after the intake valve closes. After that is a simple matter of using a standard feeler gauge and set the valve lash at .004 for both the intake and exhaust valves. How do you do that you ask. Its simple really just take your 9mm wrench and loosen the locking nut on the valve tappet. Then you loosen the tappet until you can get your feeler gauge between the tappet and the valve stem. You want to tighten the tappet down on the feeler gauge snug but not to tight. You want to be able to pull the feeler gauge out but there should be resistance. Use a pair of needle nose pliers to hold the head of the tappet and tighten down the locking nut. Repeat on the other side and put the valve cover back on. Once you get the motor back together you want to start it up and listen for excessive tapping from the valves. A tick is ok a loud tap is a problem. If it sounds weird start back at step one and try again.
|
|
|
Post by csabner on Apr 25, 2009 17:06:09 GMT -5
I have a Yamati Strada RX 150 TE....it has the Gy6....is this the very same procedure? Mine is a 2006 with 5,000 miles. if I give it full throttle, it just boggs down and I have to let off the throttle completely. It used to go 65 mph, now I am lucky to go 30...But it starts like new, and idles just fine!
|
|
|
Post by Enviromoto on Apr 25, 2009 22:49:28 GMT -5
Yep pretty much.
|
|
|
Post by scooterboo on May 14, 2009 1:47:44 GMT -5
What is a "feeler gauge" and how do you "set the valve lash at .004" im a complete newb.
|
|
|
Post by crazyivan on May 14, 2009 8:44:09 GMT -5
Feeler guage: Setting the valvelash: discrobed above, cant explain it easier what you are setting is the gap between the tappet(black threaded screw with a nut around it at the end of the rocker arm) and the top of the valve stem. .004 is thinkness of the gap in inches
|
|
|
Post by scooterboo on May 14, 2009 13:06:12 GMT -5
Ahhh I get it now, thanks.
|
|
|
Post by tortoise on May 14, 2009 13:37:13 GMT -5
how do you "set the valve lash at .004" Insufficient valve lash clearance may prevent proper valve seating, resulting in loss of compression, and combustion "blow-back" pressure through the valve stem seals . . causing excessive valve chamber oil mist venting to the inlet air filter box (possibly wetting the element). Keep in mind that everyone has their own valve lash clearance preferences, for various reasons. My stock 139QMB runs just fine with a .002" lash, and makes a slight ticking sound with a .003" lash. Installing a larger displacement cylinder kit may increase engine operating temperatures (more valve stem length expansion = less lash clearance), so a larger .004" valve lash clearance may be prudent in this application. Normal valve-to-seat "wear-in" will also reduce lash clearance. Valve lash adjustments should always be made on a cold engine . . below 95° Fahrenheit (35° Celsius). If the 3 cam-sprocket holes are aligned properly, verifying the position of the flywheel "T" mark is unnecessary. After making the adjustments, rotate the engine a few revolutions, re-align the cam-sprocket index marks, and recheck the clearances. For the 139QMB 50cc engines, the valve clearance specification is .04 mm [ .002 inches] per section 3-5 of this service manual. 50cc video guidelines (German audio). The wall thickness of an aluminum beverage can is approximately .0035 inches (.089 mm). For the GY6 125/150cc engines, the clearance range is .08-.12 mm [ .003-.005 inches] per page 9 of this service manual. 125/150cc cam-stopper issue. 125/150cc video guidelines. Rotate right-side fan with a socket wrench to align cam sprocket. Where clearance allows, a tap wrench (with or without handle) also works well for turning the adjusters. Also consider applying Armor All (or similar product) with a foam brush to the valve cover O-ring and carb diaphragm to keep the rubber supple. Try using the rounded tip of the thickest feeler gauge in the set to pry the O-ring out of the cover groove, as compared to a knife point or screwdriver tip which might damage it. On a cold engine . . while the diaphragm-slide-needle assembly is removed and the enricher passageway is open . . one CV carb cleaning method is an in-place flush (some of the newer carbs are assembled with tamper-resistant fasteners). While wearing eye protection, spray carb cleaner (aerosol can with nozzle tube) down the main jet. Temporarily rotate up the left-side L-shaped black carb bowl vent tube and plug, pinch, or clamp closed while pulse-spraying to force some of the solution through the low-speed jet and enricher passageways. Removal of the under-seat tub may be necessary for best aerosol can orientation. Several nozzle tubes can be connected with short sections of ball point pen ink tube. This procedure may wet the spark plug, so the engine may not restart for several hours . . unless the plug is removed to expedite airing-out the cylinder. To avoid this, the flush can be performed with the scooter on the center stand while the engine is running and diaphragm-slide assembly removed. As the throttle is opened to increase engine speed, pulse spraying carb cleaner down the main jet, to flow the mixture out of the low-speed port, will keep it running. Probably a good idea to change the engine oil following this procedure, in case any of the cleaning solution has worked past the piston rings and diluted the crankcase oil. Walmart sells a metric wrench set that includes a 17mm for the bottom oil drain plug, and a 9mm for valve adjustments. A small cresent is also useful for turning the square adjuster. Harbor Freight feeler gauge.
|
|
|
Post by lostintexas08 on Sept 19, 2009 2:27:01 GMT -5
very informative thank you
|
|
|
Post by lostintexas08 on Sept 27, 2009 1:17:36 GMT -5
it worked
|
|
|
Post by markyn50 on Sept 28, 2009 20:21:39 GMT -5
My scooter has 900 miles on it with the 139qmb 50cc engine. About 3 weeks ago it started acting up, died at stop lights and really hard to restart, no power and was making me crazy. I tried everything from carburetor adjustments, new fuel filter, new spark plug and nothing helped. After reading these posts I tried a valve adjustment and woolah ran like never before. Set mine to .005mm and that seems to be perfect, excellent acceleration and runs a steady 40 and gets there in a hurry. If anyone else is having my problem adjust your valves and your problem will be solved.
|
|
|
Post by Scootless Wonder on Sept 28, 2009 21:07:13 GMT -5
Why is this not stickied yet??
DEFINITELY boneworthy. Have one from me Enviro. That trick with the Armorall I NEVER would have though of. GREAT info all over in this thread.
|
|
|
Post by arigold on Jan 10, 2010 16:08:38 GMT -5
What if you don't have a T or a timing mark. I am a complete newbie who has been lurking and searching... and reading... and more reading...
Trying to do valve adjustment on 2 stroke Minarelli. I know this is different engine. But principle should be the same right?
Is there no timing on a two stroke?
|
|
|
Post by Bluefront on Jan 10, 2010 16:25:37 GMT -5
^^^^Lucky you. 2-Stroke engines don't have any valves to adjust. Timing marks....can't help you there. There may be no way to adjust the ignition timing anyway.
|
|
|
Post by 90GTVert on Jan 10, 2010 17:46:40 GMT -5
arigold, your engine uses the piston to open and close the ports. ;D It needs no valve adjustment. While you're doing all that reading, check out this article to explain how your engine differs from the four strokes... www.49ccscoot.com/guide2strokes.html
|
|
|
Post by arigold on Jan 10, 2010 17:47:32 GMT -5
Lucky me huh.... I can't figure this deal out...
Will start a new thread instead of hijacking someone elses.
Thanks for the reply.
It sucks being the new guy.
|
|
|
Post by arigold on Jan 10, 2010 19:05:46 GMT -5
Thanks for the additional information overload 90GTVert. Very much appreciated. I would rather start at the beginning and work forward instead of working backward. I had scanned through that article late last night looking for the info I needed. Who would have thought it was right in the beginning of the article.
|
|
symmike
Big Dawg
2008 SYM RV250, dark grey, 23,000 miles
Posts: 20
|
Post by symmike on Jun 9, 2010 21:29:39 GMT -5
I have a SYM RV250. It is hard to start and I have to give it some throttle to start it now when it is from a cold start. It starts normal when the motor is warm. Would I have to do this procedure or is it something else? It has over 15,000 miles now. Thanks!
|
|
|
Post by qwertydude on Jun 12, 2010 10:43:12 GMT -5
I would guess never having adjusted valves at 15,000 miles you're way past due.
|
|
|
Post by fishrfun on Jun 14, 2010 15:43:09 GMT -5
After reading this I am wondering now if My clutch and drive belt are bad or if I need to do a valve adjustment. I just got a chinese build gy6 1p39qmb with only 726KM on it and not it had 2400km and runs like crap used to idle perfectly stalls unless I keep it going. Slow acceleration. Thanks for the food for thought.
|
|
jren
Junior Dawg
Posts: 6
|
Post by jren on Dec 1, 2010 8:50:55 GMT -5
I also have one your standard gy6 chinese scooters that I would never start up easy. I bought it used with 1300 miles on it 3 months ago and have been going crazy cleaing CARB, chaning fuel filter, battery, spark plug, and ignition coil. Me being a small engine newb and a geek I found this web-site to be the only source of good information. So I came across the link for Scooter Wont Start on the scooter troubleshooting page. www.scooterfocus.com/scooter_troubleshooting.htmlScooter focus says you need three things spark, gas, and compression. Having toyed with my scooter I was convinced I had spark and gas. So under compression is valve adjustment. Well I got brave enough, went out, bought a feeler gauge and presto my scooter starts up perfectly. The top adjustment screw was already at 0.005 but the bottom one was very tight. So it took a few counter clock-wise rotations to get it to be at 0.005. Problem is that it was clanking pretty loud. So, i opened the crank case back up and only adjusted the bottom one to .004. The clanking got better but still pretty loud. My last adjustement I made was to have the gap at 0.0 and the clanking went to a tick. What the worst case scenario? Could I break something?
|
|
|
Post by larry001964 on Dec 1, 2010 9:50:40 GMT -5
Hi Jren. That 0.005 seem a little high to me, kinda near the outer limits. Current setting on mine are intake .003 and exhaust is .004.. I too em getting some unwanted ticking and em seriously considering changing the .004 to .003..
|
|
|
Post by Bellard on Dec 1, 2010 10:07:38 GMT -5
Question I have this engine if I got a bkk kit from 50 to 80cc should I adjust my valves and if so to what is safe? And do.I need the gasket for the valve cover?
|
|
|
Post by djeeper on Dec 1, 2010 10:53:05 GMT -5
any time you do anything to your engine... you have to adjust your valves. If you are asking this question, you might want to reconsider doing the BBK. You have to feel the ring gap and what not as well...
|
|
|
Post by Bellard on Dec 1, 2010 11:18:58 GMT -5
The bbk is already installed the Guy that did it didn't adjust my valves
|
|
|
Post by djeeper on Dec 1, 2010 11:34:17 GMT -5
it only takes like 2 minutes to adjust your valves, haha. just do it! its easy and quick to mark off the diagnostics list.
|
|
|
Post by Bellard on Dec 1, 2010 11:44:07 GMT -5
Bt wont I need to buy another gasket.. and considering I have stock head stock muffler with a 80cc bkk is 40mph good? Can I get better speed with a valve adjustment? And if so what should I set each at?
|
|
|
Post by erictheviking666 on Dec 1, 2010 12:32:12 GMT -5
No you don't need a gasket, the OEM gasket is rubber. You won't get any extra speed from a valve adjustment. But, you need to open up that stock muffler because your not moving enough air with an 80cc kit, 40mph is not good. Drill 2 or 3 holes in the back of your muffler, especially after you upjet. Your putting more fuel and air into the motor but your strangling it with a stock muffler.
|
|
|
Post by Bellard on Dec 1, 2010 12:39:32 GMT -5
What size hole do I drill?
|
|
|
Post by erictheviking666 on Dec 1, 2010 16:49:10 GMT -5
Whatever you think is best. I drilled three 3/8" holes in the back of my original exhaust and it worked pretty good. Although with an 80CC kit I think most people would recommend you put a free flow high performance exhaust.
|
|
|
Post by 50seesee on May 12, 2011 9:46:08 GMT -5
I gotta question about the valve clearances! I have the GY6 manual open in another tab and it says both the exhaust and intake should be set at .005 inches. Everywhere on the internet says something different. Which numbers should I use? I don't wanna experiment and end up breaking something.
|
|