[reneeangel]

I have a 2002 CRF 450 Athena big bore motor with a stage 3 hotcams setup in a cage kart. I am totally new to these motors but I've been racing karts for 28 years now (2 strokes). I've got a couple questions/issues that I'm hoping the experts out there can help me with.

1) it has the factory ignition module still...what is the rpm limit?

2) we were tuning the jetting off the plug color and it was still white after several jet changes. We installed the biggest 230 jet and it was still to lean (plug still white). What other jet(s) should I look at adjusting? The air was very very good this past weekend (corrected altitute of 500 ft) but IMHO I don't think that's the issue. The water temp was ~120 degrees.

3) On the carb, the hot start cable has been removed. Any tips on getting the motor refired "easily" without this when you spin out and stall the motor? You push start these cage karts with a quad. I know to never touch the throttle but it seemed like it was really really hard to get the rear tires spinning again when pushing it.

4) what exactly does the tps do?

It seemed to pull really hard off the corner and about 3/4 throttle would stumble and sometimes pop. The motor has been sitting for about 1 year. I'm thinking it's carb....but maybe valve springs...or rpm limiter (thus the question above). We dropped the gearing and it still did the same thing. Valve lash is spot on adjustment as well. Ideas? I can provide more jet info if needed.

Thanks!!!

Renee

[Asmith]

Welcome to the site!

1) it has the factory ignition module still...what is the rpm limit?

The rev limiter kicks in around 11,000 rpms.

2) we were tuning the jetting off the plug color and it was still white after several jet changes. We installed the biggest 230 jet and it was still to lean (plug still white). What other jet(s) should I look at adjusting? The air was very very good this past weekend (corrected altitute of 500 ft) but IMHO I don't think that's the issue. The water temp was ~120 degrees.

A heavily modded 450R engine should be running a main jet in the 180-190 range. The pilot (or slow jet) should be a 45 or 48. The needle should be a NCVS or something close on the 4th or 5th clip.

3) On the carb, the hot start cable has been removed. Any tips on getting the motor refired "easily" without this when you spin out and stall the motor? You push start these cage karts with a quad. I know to never touch the throttle but it seemed like it was really really hard to get the rear tires spinning again when pushing it.

The hot start is there for a reason because these engines flood easily when hot. Why did you remove it? You can put in a hand operated pull knob on the hot start if that would work for you.

4) what exactly does the tps do?

The TPS (throttle position sensor) tells the ICM where the throttle is so it can advance the spark curve for maximum power.

It seemed to pull really hard off the corner and about 3/4 throttle would stumble and sometimes pop. The motor has been sitting for about 1 year. I'm thinking it's carb....but maybe valve springs...or rpm limiter (thus the question above). We dropped the gearing and it still did the same thing. Valve lash is spot on adjustment as well. Ideas? I can provide more jet info if needed.

Thanks!!!

Renee

It could be any of those things, it's not a characteristic of the engine. These engines pull hard and clean to the top when properly set up. Perform a leak down test to determine the general health of the engine and go from there.

[reneeangel]

Thanks for the info ~!!

The hot start was removed by the previous onwer...not sure why.

[vector911]

Never had to use the hot start on my 2005 450R. Considered removing mine last time I pulled the carb because of it.
Previous owner might have felt the same way.