GY6 Engine coughed, then died By Steve (Read 9,707 times)

[Steve]

BMS Romans 150cc (GY6) 122 total miles. Had it all checked out a couple of weeks ago. No problems. Last week, I lost all of my gas due to a cracked hose. I replaced it and all is well. Rode it a bunch of times. Rode about 50 miles this past week.

Then... Rode 3.4mi 15 (?) min 30mph tops Thursday afternoon. No problems. Friday afternoon 3.2mi 8 min hit 50mph once or twice. Going 40-45, engine coughed then died. Tried to start it a few times. Waited a couple of minutes. Tried again (2-3x?) and it started. Drove 2.1mi about 7minutes. Went inside store (5 minutes). Started scooter and headed home. Went 4.2 miles about 10 minutes. 40mph(?) engine coughed then died. Again, tried a couple of times. Waited a couple of minutes. Tried again (2-3x?) and it started. Went home (1mi 3min).

I try to ride everyday...not today. Need help. Where do I look? Should I wait to see if it happens again?

I appreciate all input. Thanks!!

< Steve >

[tvnacman]

Sounds like it needs a valve adjustment .

John

[Alleyoop]

Valve adjustment and or running to Lean and after it gets hot under load it dies.

If the carb has a FUEL RATIO MIXTURE screw turn it counter clockwise 1/2 turn and see if that helps.
Alleyoop

[Steve]

Thanks, guys! And for the speed of the replies!

OK - so I'm a nubie... Why would an engine with only 122 miles on it need a valve adjustment?

Fuel mixture I can understand...

Do appreciate the help!

< Steve >

[jct842]

The heads are soft aluminum. No hardened valve seats just soft aluminum. The valves sink deeper into the head untill head gets work hardened. You will find the gap just closes up in both but exhaust more so. john

[tvnacman]

I like to do a valve adjustment fresh out of the crate . I don't think it is ever too soon .

John

[Steve]

I tried the adjustment ( quasi per Alleyoop). It was more than 2 1/2 turns out. Screwed it in and backed it out 2 1/4. Darn thing quit on me again. It really seems as though it only happens under a load when it gets hot... If I let it cool down for a few minutes, she's fine...until she gets hot again.

I guess hot aluminum would act the same... If it's a valve adjustment, are they expensive? Where do I get a manual or instructions? I'm really not sure I can handle it... :-(

Thanks!!

< Steve >

[tvnacman]

there is a good video around let me see if I can find it and I will post it . Very simple you will see once you watch the video .

John

[Steve]

I hope so! It looks to me like I have to pull the engine... Time to find a mechanic! ;-)

[gatekeeper]

Here is a video. You don't really have to worry about taking the fan cover off to line up timing marks. Just make sure the holes on the cam sprocket line up as shown so that the rocker arms are on the backside of the cam lobes. Adjust the valves with a cold engine.

scooterdoc.proboards.com/index.cgi?board=videos&action=display&thread=4730

Shouldn't have to pull the engine, maybe a few body panels.

[Alleyoop]

Just get yours self feeler gauges any autoparts store make sure the set has .003 inchs, 004 inchs and .005 inchs.
Set them both to .004 inchs and it will be fine.
Just take your time the first time may seem scarey but after you adjust them the 1st time the next adjust will be a breeze.
Alleyoop

[Steve]

Not that I need to say anything...but you guys were RIGHT! The intake valve would not even accept a .002 gauge and the exhaust valve was too far out for the .005. The video was pretty good, too.

Question: Is there a gasket or sealant that is needed when you put the valve cover back on? NONE of the videos I have watched even mention it...

Thanks!

< Steve >

[jct842]

Most metric combination wrench sets do not include a 9mm wrench. I don't know about other people's scooters but my 150 needs a 9mm wrench for the nut locking the valve adjustment.

[mrpalmetto]

You can buy a craftsman 9mm wrench on Ebay delivered for $1.75. Unbelievable!!

[Alleyoop]

If you look the VALVE COVER has a gasket that goes in a slot all the way around the valve cover. Just do not go and CRANK on the valve cover bolts just nice and snuge and tighten them CRISS CROSS, top right-left bottom, top left-bottom right etc..
Alleyoop