GY6 Engine coughed, then died By Steve (Read 9,689 times)

[Steve]

Appreciate all of your suggestions/input. It is still not performing as I think it should. My mechanic told me to take it easy with it for the first 300-500 miles. I didn't realize I was too rough on my little scooter...but, I'll treat it better this week and see if it performs better. Next thought (from my inexperienced mind) is to adjust the mixture. I set it at 2 1/2 turns. Think I'll try three...

And...from the minds of you guys?

< Steve >

[kepps1280]

My BMS had similar problems last year. Had about 75 miles on it. Turned out to be a $12 fuel pump. Everyone ignores the fuel pump in diagnosing problems, but it is a very important part of the system

[Moat]

Hmm, I dunno... but an engine that noticeably COUGHS, then dies abruptly, would make me suspect ignition. Myself - I'd first replace the spark plug with a good NGK and inspect all of the coil/plug cap/plug wire/CDI wiring/engine-to-frame ground wire for any bad/loose connections. But heat may be exposing an intermittent failure in the CDI, HT coil, trigger coil or stator windings (if the CDI is AC).

[Steve]

kepps1280: Fuel pump sounds logical.

moat: I wouldn't say it dies abruptly. It slows down when it's coughing...and then it dies. I haev a new plug. The mech changed it when he did the valve adjustment. I check electrical connections as a rule of thumb. My mech also talked about the CDI... How do I know if it's AC?? It has a 12v battery!!!! See how ignorant I am.

Edward from BMS Motors Part Dept said that Valve Clearance should be (00.6 - 00.8 IN-EX). Guess I need to go back in...

Still haven't turned it the extra 1/2 turn.

Really appreciate all of the help!!

< Steve >

[Cruiser]

Hi Steve. You might want to change the valve clearance that was given from (00.6 - 00.8 IN-EX) to .004 inch for intake and .005 inch for exhaust valve.

[Steve]

OK - I have just stripped it down to the valves...for my first time. Came in to verify EX is on the bottom...

Cruiser: I was just getting ready to measure the current clearance. I presume it's at 4&5 already - and still has the problem. The BMS guy said 6&8. ALL you guys say between 4-6. Oh, well. I'm ready to do it.

Reply QUICK if you think I'll break the machine. ;-)

< Steve >

[Alleyoop]

Go for it, most of use set the TOP INTAKE to .004 inchs and the BOTTOM EXHUAST to .005 inchs. Some go little wider on the EXHAUST so it last a little longer to .006.

But if you gap them to wide they will CLATTER and you know you have them set to wide of a gap. TO QUITE and they may be to tight, a LITTLT TICKY TICKY TICKY noise is good not to loose and not tight.
Alleyoop

[Moat]

May 22, 2013 17:16:59 GMT -6 Steve said:

My mech also talked about the CDI... How do I know if it's AC?? .....

...Edward from BMS Motors Part Dept said that Valve Clearance should be (00.6 - 00.8 IN-EX).

From the Scooter Doc Library, here's a post about identifying CDI's - scooterdoc.proboards.com/index.cgi?board=electrical&action=display&thread=4996

And like these guys already mentioned, those valve clearance specs you gave us should actually read 0.06 - 0.08 mm (millimeter) - which would be about .0025" - .003" (thousandths of an inch). Yes, .004" - .005" would be fine/safer for now... if maybe a little noisier.

[Steve]

OK. I heard CLATTER...and I don't think it was the reindeer...

I measured before I started. IN - .003 EX - .002 (maybe) It was tight. Interesting.... Maybe he didn't hold the vslve tight. Who k ows.

So-o-o, I figured I would set them to 4 and 6. I did. It sounded OK. But that was before I put the fan cover back on and the lower hose to the valve contraption. Put it all together; took it for a test ride. After about 2 blocks, I turned around and came home.

So-o-o, I'll change the EX to .005. Yes, I'll measure them first. ;-)

After all, tomorrow is another day!

[Alleyoop]

Nice going, if you still do not like it at .005 on the Exhaust you can go .004 on both which is what I use on both valves. Now you know what works, not to loose and not to tight for next time.
Alleyoop

[Steve]

Next?

The clearances did not move. I consider that a PLUS! I do GREAT work.

More edumacation please. The lower valve arm has a little play in it. Yes, the holes are lined up as they are in your video. So-o-o, I go to the fan...

The fan markings are: | | F T |

I turned the fan to where the mark is opposite the "T" line - the fifth marking. The lower arm is tight at that point...but the three holes are not lined up at all.

Which is important?

And, where to from here?

Thanks!

< Steve >

[tvnacman]

I have an idea for you , while the engine is warmed up and running . Slip your finger under the carb and pull it up from the back (gently) . just flex the rubber a little . See if the engine has a change in sound or rpm . When you do this you need to hold still for at least 20 seconds and listen . Flex it to the left and right . The rubber is known for cracking and leaking . Sometimes flexing it will show a crack or leak . (show meaning a change in sound or rpm)

John

[Steve]

Can do. When I put it back together after the valve adjustment.

Thanks.

[Alleyoop]

Do you not mean that the FLYWHEEL MARKINGS ARE LIKE THIS:

1.The fan markings are: | | T F |
2. and NOT The fan markings are: | | F T |??
Alleyoop

When the CAM HOLES are lined up with the top of the HEAD.
The CASE POINTER should be pointing Either Right before the "T" or maybe the LINE BEFORE THE "T".
Alleyoop

[Steve]

I had to go check. And I took a picture. You're right. But you knew that. ;-)

L to R: | T F | |

With the holes lined up, the line to the left of the "T" is about 3/8 to 1/2" above the mark.

How do I get you the pics? They are jpg and pdf. What do you prefer?

< Steve >