How to tell if a cdi box is bad??? - Snowmobile Forum: Your #1 Snowmobile Forum

Kaw_rcr · 03-21-2008, 11:18 AM

How do you tell if a cdi box is bad? if the sled doesnt start?? thanks

Spun222400 · 03-21-2008, 12:29 PM

are you getting spark?

Kaw_rcr · 03-21-2008, 01:41 PM

the snowmobile works fine, i just have an extra cdi box and i want to know how to test it , to see if it works.

**smallengineguy** · 03-21-2008, 02:21 PM

Swap it onto the good sled and see. Only way to check them. If it doesn't start, it's junk.

TCOLLINS · 03-21-2008, 03:27 PM

The way I knew mine was bad is that The sled ran like crap. I than took off wires one at a time and realized it was only running on 1 cylinder. Then swapped wires than other side worked. I did have spark on both cylinders but one was very weak. Sled still started right up but didn't run too well(on 1 cylinder). So to test cdi I would unhook each plug wire individually and see if it starts. It will start one 1 wire. If it only works on 1 wire than its probably bad.

tylerbrannam · 01-18-2010, 12:20 PM

my 1991 Yamaha Phazer II480 drops cylinders at top end i think its the cdi box what do u think every thing is new exept for that

Blaine1 · 01-18-2010, 02:26 PM

Quote:

Originally Posted by smallengineguy

Swap it onto the good sled and see. Only way to check them. If it doesn't start, it's junk.

x2. Pretty much the only way...

tylerbrannam · 01-29-2010, 04:12 PM

well my friend has the same sled and the cdi is just fine what else do u think it might be

razor_burn · 01-29-2010, 08:26 PM

You'll have weak or no spark.

tylerbrannam · 01-29-2010, 08:31 PM

aks like it runs out of gas good spark other than that im thinking the fuel pump is goin bad

Blaine1 · 01-30-2010, 06:01 AM

Quote:

Originally Posted by tylerbrannam

my 1991 Yamaha Phazer II480 drops cylinders at top end i think its the cdi box what do u think every thing is new exept for that

Probably not the CDI. Either bad coils (Have you trimmed the plug wire ends?), stator or fuel issue. Check the compression too. Does it do it all the time? Only after the sled warms up? ect..need more info.

SnoCat800 · 01-30-2010, 09:26 AM

Somewhere I read that the spark plug should always be securely grounded when checking for spark otherwise it could destroy the CDI. Wouldn't that be possible if you just disconnect the plug wire?

tylerbrannam · 01-30-2010, 07:07 PM

the plug wires were not trimed coils are new the stator is new im goin to take off the fuel pump and check it in a friends sled and see what happens

jwaldmann89 · 01-30-2010, 10:26 PM

Quote:

Originally Posted by SnoCat800

Somewhere I read that the spark plug should always be securely grounded when checking for spark otherwise it could destroy the CDI. Wouldn't that be possible if you just disconnect the plug wire?

That doesn't really make sense to me...pretty sure CDI boxes just hold a charge and up the voltage, then disperse it at the right time to the coil that up's the voltage more and sends it to the plugs...not sure how having them not grounded to the engine would hurt it, it has a ground coming out of the bottom of the CDI box right to the motor. But I could be totally wrong, this is just my opinion/observations

SnoCat800 · 01-31-2010, 01:06 AM

Quote:

Originally Posted by jwaldmann89

That doesn't really make sense to me...pretty sure CDI boxes just hold a charge and up the voltage, then disperse it at the right time to the coil that up's the voltage more and sends it to the plugs...not sure how having them not grounded to the engine would hurt it, it has a ground coming out of the bottom of the CDI box right to the motor. But I could be totally wrong, this is just my opinion/observations

Come to think of it, pretty sure it say's that in the 90-98 manual. Believe it say's it's "possible". Take your chances.