My travails with a 260 Linhai By scjbob (Read 4,784 times)

[scjbob]

I bought this scooter new about 18 months ago. I failed to do a full PDI at that time. I put 300 miles on it and it has decided to refuse to start. It cranks fine. Gets spark. Fuel flow OK. So here's what I have done so far:
1) removed, cleaned and reinstalled carb
2) checked all fuel and vacuum lines. I'm in the process of replacing all of them with real American rubber. Several clamps were missing so I am now using zip ties.
3) replaced a leaking fuel filter
4) discovered a broken filter in the fuel line going from the top of the gas tank to the charcoal cannister (anti-fuel spill) and replaced it.
5) Adjusted valves. They were a little tight because I could not get a .004 into the intake side or a .005 into the exhaust side. All is good now
6) checked the enricher (functions properly)
7) attempted to adjust idle at several different levels. I did this prior to removing all the panels and commencing with the PDI.
8) changed oil but still need to change radiator and crankcase fluids.

Once I'm finished with the hoses and fluids I'll hook the battery back up and give her a go. Am I missing anything?

[JR]

For sure you're getting close to a full PDI I would just add go through the electrical connections and plugs while you got it stripped for bad connections, loose wires etc.

Ok lets start with some basics and please bear with me as I ask these questions.

You say you have spark, a good strong blue looking spark or a weak looking yellow/orange type spark?

You say good fuel flow are you refering to getting good gas flow to the carb?

We all know you need fuel, spark, air and compression for an engine to run and when you say crank you mean it'll turn over but not start and run right?

If this is the case then as with all things we eliminate one thing at a time until we find the gremlin.


So if we have a good blue spark then lets see if fuel is getting through the carb to the spark plug? For me the easiest way to eliminate this gremlin is to pop off the top vacuum hose on the intake manifold and spray a good squirt of carb cleaner in the port, quickly put the hose and turn it over. if she starts even just momentarily then we know we have a carb issue even after cleaning.

If she still won't hit a lick then lets check the compression, a simple test is to pull the plug and put your thumb over the hole and crank it over and if it blasts your thuimb off then all is fine but you can still use a tester and see what you have? This engine should be 150PSI or greater.

If we have very little or no compression then we have a valve not closing all the way or we wasn't on TDC on the valve setting or worse yet extremely bad piston rings?

So this is a few things to look for and we'll take it a step at a time untill we find this problem.

JR

[scjbob]

Funny that you ask about the spark. When I checked it I thought it appeared a little weak. Certainly wasn't a strong blue spark. What would a weak spark indicate to you?

And I am getting good fuel flow to the carb but maybe my method is suspect. I pulled the fuel line from the carb, cranked the engine and saw a pulsating stream. When I removed the carb it had about an ounce and a half in it. I never smelled a strong fuel odor so I don't suspect flooding. The plug was not wet when I removed it either. I squirted about 5 ccs of fuel into the top vacuum port but still didn't get any combustion. That kinda threw me for a loop.

I haven't checked for compression but I did adjust the valves. I made sure it was at TDC when doing so. I was unable to get the feeler guage to slip between the valve stem and the tappet. (am I describing this correctly?) So I adjusted both according to the clearances called for on this engine (.004" on the intake side....004"-.006" on the exhaust side. I settled for .005" there)

I just haven't completed everything to retry starting it yet. I probably won't have time to get to it again until this weekend. But thanks for the help. I'll post an update when I have one.

[JR]

A weak spark would indicate a weak coil, bad connection on the coil or CDI or might be a weak CDI. Even need to check the grounding of both units.

But even a weak spark should at least let the scooter fire providing it's geting fuel and since you sprayed fuel in the intake vacuum port we know it got some fuel.

Again we need to check the compression of the engine and do check out the wiring of the coil and CDI.

JR

[scjbob]

Hi JR,

Well I finally had some time today to finish off all the vacuum and fuel lines. After reinstalling the airbox and hooking up the battery I tried to start it again. Still cranks but no start...So I pulled the plug again and checked for spark. (By the way the plug is not wet but I can smell fuel on it.) Now there is no spark at all so it looks like the cause of the weak spark has become pronounced. While I had the plug out I checked compression with the simple thumb method. It blows my thumb right out of the hole. So now I'm suspecting that it could be the coil, the CDI or the connections to these components.

That being the case I am now in uncharted diagnostic territory. I've never been good with solving electrical problems. Where should I start? (assuming that I have already checked the connections and they look fine).

In my next post I will attach a picture of the CDI and it's 5-wire connector.

[scjbob]

The wire color coding is:

*Open *Black/Brown *Open *Open
*Blue/Yellow *Green *Black/Yellow *Green/White

I have a nice multimeter but not much experience using one. I saw a sticky post of your on the basics of CDI, Coil and Stator. I assume I need to check for voltages and grounds beginning with the CDI. But the color codes on my CDI don;t match any of the colors in the posts on the website.

Bob

Attachments:

[JR]

Good picture and you have the single plug 5 wire CDI which is DC powered and here is the wire code:

black = 12vDc from ignition
green= ground
black/yellow = coil feed wire
blue/yellow = stator trigger or pickup wire
green/white = engine kill wire

Now before we just start buying parts let's do a couple of tests. With the multimeter unplug the CDI and turn the key on and check the black and green wires with the meter, you should get 12vDC+ if not then we got to find out why? Bad wire or connection but this is how the CDI gets power. If you have voltage:

Next test the black/yellow wire while turning over the engine, you should have good strong voltage if not do this last test:

Unplug the green/white wire from the plug and then check to see if you have spark, if so then you've got a bad engine kill switch on the handle bars, a bad ignition switch on the kill side or the green/white wire is open and touching ground somewhere. The green/white wire kills the engine by grounding out the CDI so if the wire is touching a ground source no spark.

If you don't have a spark after doing these 3 tests then you have a bad CDI, if the CDI is putting out strong voltage on the black/yellow wire then you either got a bad wire or bad connection to the coil or the coil is bad.

Let us know what you find out.

JR

[scjbob]

Thanks JR. I have a crazy week and will be traveling from this coming Wednesday through the following 10 days so I will not be able to get to the tests on this CDI/Coil for a time. But I will update you when I get back home and give it a go. Thanks for the help. I'll let you know what I find.

[rp]

This seems to be the exact problem I've had with my MC-62. I,ve got a new coil on the way now and hope that resolves the weak spark issue. The reason I was not getting any spark was because of bad connectors. (Poor PDI) Take the female end of the connector and push a small screw driver into it to compress the metal end. The connectors on my scoot have a little cut out on the side I put the screw driver in. The connectors use to come apart very easy.
now their a lot tighter. Hope this can help

[scjbob]

Thanks for the tip. Now that I am back for a few days I will try to find some time to attack this. The summer is quickly leaving us and it would ne nice to put some miles on this scooter.

[scjbob]

OK. After all this time I finally got the scooter started! It took a new coil to make it happen. Now that I have it running I am experiencing bogging when hitting the throttle. Here's the scenario: Body panels are still off the frame. Needs to idle at about 2000 to keep it running. While on the center stand I throttle up to about 4,000-5,000 and it wants to bog. Where should I start? Fuel mixture screw? Keep in mind that I've already cleaned the carb (twice), replaced all fuel and vacuum lines, adjusted the valves, tested the enricher, and checked/tightened electrical connections.

[Ernie]

The easiest thing to do is pop the cap off of the low speed idle mixture screw which is directly underneath the side of the carb that connects to the motor. Crank it all the way in(clockwise) then set to 2.5 turns out. This is where JR says the starting point is. You need to tip the carb with the bottom 90 degrees toward you to get at the screw by loosening the collars on either side.

Ernie

[scjbob]

Ernie,

My Linhai carb has the low speed idle mixture screw located on the side surface of the carb so I did not need to remove the carb to get to it. I set the screw at 2 1/2 turns and viola! It not only started right up, it didn't bog as I hit the throttle and took it to about 4500rpm. Now I can install all the body panels and road test it for fine tuning. I'll give you a road test report when I'm done. Thanks to JR, you and the others for all the helpful hints. This is a great site. After this long series of diagnostic tests and adjustments I feel like I now have an undergraduate degree in Chinese Scooterology. I hope I won't need a graduate degree to solve any future problems. Cheers!
Bob

[scjbob]

OK. Took it out for a low speed test ride. It seems to want to bog down a little when cruising at low speeds (10-15mph) I only took it up to about 40 so I haven't tested WOT yet. Won't be able to for another 2 weeks though due to travel schedule. It idles pretty good at about 1500. But with the low speed bog issue I suspect I'll need to fool with the slow idle screw to get it just right?

[JR]

1500 is a tad low Bob set her at about 1700 and I think it'll help a lot on that low speed bog?

JR