Logo
FULL SITE MENU

1998 100hp 2 Stroke - miss at 4300 rpm getting worse

J

jimmysbay

New member
Hi,

I have had this motor for about 15 years now, and for the most part it has been great.

Ever since I got it is had a slight miss around 4300 rpm, sounds like a cylinder drops out and
at first it was very specifically at 4250 to about 4300 rpm, but will run ok below and through it up to 5000 rpm.

over the years, the "dead zone" has slowly expanded.
after years the band increased to about 100 rpm, the 150 now is abut 200 rpm.

we have done a lot n the fuel side over the years with no change to this issue. 90% sure it is electrical.
added an inline fuel/water separator, cleaned and set the carb many times, replaced internal fuel filter, spark plugs annually.

The CDI ox was replaced once about 10 years ago as well.

The issue is bad enough now, that I think the next drop will leave me unable to get through the "dead zone" and above 4200 rpm

was going to begin my way through eliminating electrical components and was planning to start with the coil.

anyone seen this before and have any insight where to start or troubleshooting methods?

it can get pricey fast just swapping components.

Thanks !
 
First I would check all the spark plug coils - remove them, give them a really good wipe off with a rag and look for small/spider web cracks in the coil case. That is "not uncommon" at all, in the past 4 or 5 years I have replaced numerous "cracked coils", mostly on mid/late 1980's models - seems like 20 years is possibly their "typical lifespan".

If all the coils are fine I would be looking at the stator. It has low speed and high speed windings (unless you have a CDM style ignition). If you have a crack in the high speed (coil/s) it may not be pushing enough power at higher rpms.
 
Last edited:
Thanks I will check for cracks.

I may have terminology wrong, but I believe each cylinder has its own CDM box.
I will check for cracks in them, preliminary pricing is about $75 each.

part that has me puzzled, is once I get above to about 4600 rpm it runs perfect again all the way up to 5000 rpm.
 
Good point. I'll have to find a manual that gives factory ranges. Any hints on how to go about it on the stator? I'm goodwith the mechanical stuff, but not with the electrical.
 
Back
Top