Ok i started a new thread as the other one was big and really not relevant to this problem.

This is a 2000 monsoon 90cc 2 stroke. I have done the following:

1 New coil and cdi
2 New spark plug
3 New fuel filter
4 Fresh Gas
5 New rubber intake manifold (old one was cracked badly and leaked)
6 Removed dissasembled and cleaned carb
7 Blocked off oil injection hole on carb (missing tank)

It starts up and idles fine but it bogs down somthing terrible when i try to give it gas. I can get it to rev up and run ok at higher rpms if i have the rear wheels jacked up but it has a horrible dead spot in it off idle. I've played with the mixture screw (its the only adjustment other than the idle screw) the initial setting was 2 turns out and it seems to run best almost all the way in. I have noticed that if i open the screw on the bottom of the bowl it barely drips gas so i thought maybe i had a fuel dellivery problem? but im getting a nice healthy stream of gas out the fuel line at the carb. Could this be a float problem? or timming isue since im running a other than factory CDI/coil? if its timming how do you/can you adjust it?


Thanks for all your help as i would have never even got to this point if it wasnt for the helpful answers on here! hopefuly now that it actually runs i can get past this and have a nice cheap quad.

 

Ok i found this:

Engine Type

A 2-stroke CDI cannot be used on a 4-stroke scooter engine. If you have a 4-stroke scooter engine you need a 4-stroke CDI. The ignition timing is completely different between the 2-stroke and 4-stroke engines.



Does this seem to be my problem? since i took the CDI off a 4 stroke atv?? where do i get a 2-stroke cdi? and would the coil be diffrent also?

 

I started to respond to your original thread yesterday, but stopped because I wanted to research it some more.

I'm beginning to come to the same conclusion as you - the two stroke timing is way different than a 4 stroke and that the CDIs are not compatible. First I looked to see if I could find any chinese two stroke engine that used the generic chinese CDI. I could not, they all used different CDIs then those listed for stroke engines. I also could not find any 2 stroke CDis that said they also worked on a four stroke. That kind of says something.

I don't have any experience at all on two stroke engines, but after thinking about it the gas/oil fuel mixture has to burn at a different rate (i.e.slower) than pure gasoline, so the timing would probably have to be advanced somewhat when compared to a four stroke.

I did have a 2 stroke mccullough chain saw engine powered go-cart when I was a kid. As I recall the timing at idle was 18 degrees BTDC, but that was such a long time ago I can't be sure of my recollection.

Just for grins I used a timing light to measure the timing on my 4 stroke GY6 150cc engine (which uses exactly the same CDI internal circuitry as the generic 5 pin CDI even though it has different connectors on it). I got 3 degrees BTDC at idle to about 14 degrees BTDC at around 4000 RPM. To measure those degrees I had to do some calculating from the TDC mark on the flywheel and measuring the flywheel diameter. The flywheel only had TDC marks and an "F" mark. The "F" mark was where the timing light showed the timing to be at approximately 4000 RPM. At idle the timing was between the TDC mark and the "F" mark, but much closer to the TDC mark.

Using the 3 to 14 degree ignition timing that I measured I tried to find a concensus on what a two stroke timing curve should look like. I wasn't able to come up with any consensus.

So does your monsoon quad have timing marks on the flywheel? If so you could check the ignition timing with a timing light. Since the timing marks on the engine show where the spark should be, you could see if the timing with the new CDI is way off the marks. That would clinch it if that is what you see. GY6 quads have a rubber access plug in the flywheel cover to allow timing light access. Other quads have a screw plug. Some quads you will need to take the engine cover off.

At least the new CDI proves that your stator ignition power winding, pickup coil, plug, and wiring are all OK. And that your original problem was the Monsoon CDI or coil.

As far as whether the coil between the 4 stroke and 2 stroke quads is the same, I don't know. The CDIs and coils are roughly tuned together. They may work or they may not - but it doesn't hurt to try. You could always wiring in your old monsoon coil and see if it works. If it does then you know the coil works. If it doesn't you don't really know much because it could just be a bad coil, or an imcompatible coil.

 

Im going to order a yamaha jog cdi they look identical to the one that was on there and are about $20 shipped. I haven't really dumped much $ in this and more I think about it the more it sounds like it is the problem it acts like the timing is waaaay off. And throttle response is lousy for a 2 stroke.

 

Sorry all I have been out of town and out of touch for a while. I 100% agree that the CDI timing not working right because I was having the exact same issue. I could get it to rev sometimes on jack stands but i have been chasing carb issues thinking that that was my issue. DUH. It does start on one kick though so im stuck on this as well. I dont get how if its that far off it will start so easily. back to the drawing board for me as well. Im truly sorry if i had you chasing a possible dead ended solution. I can always be reached @ bwbuer@ hotmail or by text or phone. 719-200-9552

Brad

 

That's very interesting. It verifies Jacob_Royers observations, and points even more at the ignition timing being different between the generic 4 stroke CDI and the monsoon 2 stroke. I can easily see how one might think it is carburetion rather than timing. I was thinking that too.

This is one of those problems that is difficult to solve alone, but when multiple experiences come together the answer pops out. There has been several monsoon / yerfdog questions in the last few months. I'm sure this thread is going to be helpful to many others in the future.

Thanks for reporting back! .

 

Il let you guys know how the cdi works out I found a performance cdi for $ 20 shipped on ebay should be here in a few days.

 

The 2 stroke racing cdi off ebay worked! i found it by searching ebay "jog cdi" 20$ shipped to my door. Aparently the timming was the issue! very strong running little atv! just need some minor tunning on the carb. if you get into the throttle slow it bogs a little but if you just crack it open fast it runs great. I have a open element filter now and knocked the spark arrestor screen out of the muffler so maybe i need re-jetting?

 

One more thing. The new cdi worked with the generic China coil.

 

Awesome! This thread is going to help a lot of monsoon / yerf dog owners.