Installed perf CDI, still hits rev limit. Kandi gkm2

[MidnightRider]

I installed this "no rev limiter" CDI on my Kandi GKM2 and it still hits a rev limiter. Is the limiter outside the cdi or is the cdi ad lying?

http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1


Thanks

[x-bird]

hard to say, all engines that utilize coil springs to control the valves have a mechanical rev limit based on the spring's ability to compress and return at the rate of the valve events. The rev limit you're hitting could be valve float from the springs not being strong enough. or the cdi doesn't work as promised. You'd have to hook up a tach to see if you're getting more out of it.

[ckau]

I've used one of these and was able to turn upwards to 10,000 rpms. Most likely your experiencing valve float . It's typical of the small valve stock heads. Depending on the manufacturer and the age of the head ( springs get weak), you might not be able to see much over 8500,
Many years ago there was this electronic geek over at BN who attempted to discover (at the time it was a rumor that rev limits even existed) which cdi's did indeed contained a limit. There wasn't all these aftermarket" high performance" offered back then. Fellow members sent him cdi's from various models to test. If I remember correctly, or not, he found two out of about 6 that did contain a actual limiter. Don't quote me on this, it was almost ten years ago and my memory sucks. There may still be the thread in the archives over at BN. I do remember that a limiter was discovered and we were surprised at the low percentage of the test batch that actually contained a limit.
my point is.. don't dismiss that cdi yet, take a look at up grading the valve train.
Also consider these motors use a huge amount of fuel to run at high rpms. you may be jetted fine for low to mid range or normal riding but your running out of gas when it really turns up.
Kind of a tough call to make as all three, cdi, valve train, and fuel all give similar symptoms, the motor reaches a certain point then runs flat.

[ckau]

Ha! X and I posted at the same time with the same conclusion! He mentioned which I failed to, was to hook up a tach. That's going to tell you what's really going on.

[MidnightRider]

Thanks for the replies.
The engine/buggy is only 3 months old so hopefully she's not tired yet. It hits the limiter hard, esp downhill, and seems to be right about stock max-RPM so I feel like it's electronic.. When the limiter activates, it's an abrupt power interruption and a very audible difference.

Can you guys recommend a better CDI? (with the same plug)

[GX150]

My CDI did not have a limit, but the stock fuel line and filter were not providing enough volume at higher RPM's causing the carburetor bowl to empty.

[zman007007]

welcome midnight. is the motor on your cart a 250cc and also did you notice on the cdi site it says these are not guaranteed to work on go carts.

[MidnightRider]

It's a 150cc and yeah the ad says stuff... But this isn't that complex a part, to know otherwise. I got this one because I had trouble finding a CDI with the right plug. If it's the wrong part, I doubt it'd run at all, right? It runs just like it did with the original part.

On a steeper hill it'll cut out longer, could that be an empty fuel bowl? I'm use to tuning efi, not a carb.

Thanks everyone!

[x-bird]

Usually fuel starvation (sucking the system dry at high rpm will be somewhat like hitting the brakes .. the engine will lose rpm and slow down. Valve float, the engine will go into a "stuttering" sound. The new cdi probably put the valve springs right to their rpm limit and probably it could go beyond with better springs.

[MidnightRider]

Originally Posted by x-bird

Usually fuel starvation (sucking the system dry at high rpm will be somewhat like hitting the brakes .. the engine will lose rpm and slow down

This sounds like my problem. Thanks! I'll try a new filter and feed line. Kinda surprising it's running out of fuel even 100% stock & new.

[MidnightRider]

After trying a lot of things (filters, jets, valve adjustment) the kart ran better but still cut out at top speed. Finally tweaked the float to fill the bowl more and that solved the problem.

[maybe2fast]

I think I have the exact same buggy. I explored the CDI boxes and found that they have the square plugs rather than the round plugs. check out the thread for more info. http://www.buggymasters.com/forum/showthread.php?t=5529

[MidnightRider]

Yeah, I had the same plug problem which is how I ended up with the CDI above... turns out it works great.

[maybe2fast]

The stock CDI has no rev limiter...at least up to 9000rpm! I had the engine up there once and it wasnt making a ton of power past 8000rpm. At least the GKM-2 I have

[MidnightRider]

Oh, nice... might have to try it again to compare.

[maybe2fast]

Here is a good quote from SYCARMS about CDI boxes for buggies.

Originally Posted by SYCARMS

Timing advance in a cdi is mapped according to vehicle. The performance CDI's are mapped for scooters which are much lighter and only drive one much lighter wheel. Being the buggy is much heavier than a scooter, driving 2 wheels with a 20 pound axle the rpm's the buggy will need advance will be much different than the scooter since the scooter puts more of the engines HP to the road as compared to the buggy. Now back to the old AC cdi's some performance cdi's would give you some performance gain since the buggy come with a scooter mapped cdi. However the late model dc buggies due to EPA have to have their own mapping in order to pass certification. The timing comes in at different rpm as compared to the much lighter scooter. Unless you go with an adjustable dc cdi there will be no benefit and will most likely hurt performance some. The adjustable cdi' work great but due to using a dash pot for adjustment it's just a matter of time due to shock the timing will move and adjustment will be lost and they are expensive. I looked into MSD building one for the buggy but unless there are huge quantities ordered the cost would be somewhere in the area of $500.00. They don't use the flawed dashpot but instead a laptop is used to map timing events. The customer I spoke of in a previous post had a performance cdi on his buggy. He brought it to me with a no start after setting up for a year while deployed over seas. He was telling me how even though it had little run time on it it was lacking power after installing the cdi. The dealer he perchased the buggy and cdi from talked him into the hot coil, uni, rejet and iridium plug. Shortly after he was deployed. I cleaned his carb and stuck a stock ASW dc cdi on it and he was pleased with how it performed