88Exciter - Running FAST - Snowmobile Forum: Your #1 Snowmobile Forum

88Yama · 01-21-2006, 04:49 PM

Putting an '88 Eciter back on the snow (Father-son project).

Got my hands on a used PSI Racing exhaust from a bone-yard (Exhaust was missing when I got the sled). Cleaned out carbs (varnished beyond belief!). Now when I start it up, it revs up to redline unless I keep the choke/starter all the way "on".

I've turned the idle control out, almost to the point of falling out
and checked the pilot air screw (5/8 turn out as spec'd).
Not sure what size jets/needles I'm running or should be, or if that is even an issue here. Seems like a pilot jet issue?

I'm a bit new to this Carburetor stuff (I like to work of fuel injected CARS!-)

Any help/pointers would be greatly appreciated!

**smallengineguy** · 01-21-2006, 09:27 PM

Are the throttle slides dropping completely down onto the stops, or is the throttle cable too tight? There should be around 1/8 inch of play in the throttle lever before it starts to move the slides.

88Yama · 01-21-2006, 10:25 PM

Good question. I made sure they were lined up when I put them in. Is there a way to tell without taking the carbs (back) out to see the slides move?

mx and sled 41 · 01-21-2006, 11:55 PM

remove the air box, and put your hand into the carb and doo it by feel.

letitsnow · 01-22-2006, 10:28 AM

you will have to rejet with the pipe.

88Yama · 01-22-2006, 04:34 PM

ALL RIGHT!!!!

Thanks for all the advise folks! SEG, you called it.

The throttle cable adjusters had been backed WAY OUT.
Dunno why I didn't think of that. (Made for an interesting ride when it first started earlier this week.... That's another story. Suffice it to say: Memo to me, set the break and/or remove the belt when starting a sled with freshly cleaned carbs. You never know...)

ANYWAY, I ran them in until the cable housing stopped following. Turns out there is a ring right at the top of the adjuster, on the cable housing. Turning it in just a bit more reveals about 1/8 inch of the cable housing past the line... Cable is slack... (Makes me wonder if the previous owner tried to compensate for the grunge clogging up the carbs by just cranking them back.)

It's now running at a normal speed, holding around 1-2K rpms. Idle can now be controled by the Idle Control Screws (WHO KNEW!?)

It's a bit "smokey". I let it run for about 5 minutes or so.
Then checked the plugs. Center electrode is UPS brown and just
a bit of black oil around the outer ring... Not bad?

I hink I now need to balance the carbs. But before I go there...
How do I find out what size jets I should be running?

Thanks again, everyone!

**smallengineguy** · 01-22-2006, 04:49 PM

Main jet size is #320. There were a few optional ones offered, though. The spark plug sounds perfect. I'd keep it as is. Make sure the oiler is working properly also. Is the fuel old? Old fuel will smoke badly. Glad I could help!

**RJ Gleason** · 01-23-2006, 02:34 PM

Bad idea, the engine can "run away" and you will not be able to shut it off. the belt can help keep theis from happening and you can use the brake to slow it down so it will shut off.

Also there are warnings posted on the engine compartment against this.

FxsX24 · 01-25-2006, 11:40 PM

Quote:

Originally posted by RJ Gleason
Bad idea, the engine can "run away" and you will not be able to shut it off. the belt can help keep theis from happening and you can use the brake to slow it down so it will shut off.

Also there are warnings posted on the engine compartment against this.

what is "running away"

SergeantDHall · 01-25-2006, 11:48 PM

88 Yama,

Yamaha Exciters 87-90 ran Mukuni 38mm Roundslide powerjet carbs, and they were jetted from the factory for sea level as follows:

Left Carb - 320 main jet, Powerjet - 160
Right Carb - 320 main jet, Powerjet - 200

All the Exciters from Yamaha were jetted rich, or fat, whatever terminology you are accustomed to using, but depending on your elevation, there was alot you could do to really liven up these machines. I have two Exciters, and have played extensively with the carbs, because I could not find anyone who could give me a reasonable answer on how to properly jet the carbs for performance or mileage at the elevation I ride, and through trial and error (never burnt down either machine's motor) was able to determine what the proper jetting was for a given elevation.

It will probably surprise you, but for the altitude I ride at, which is 5500-8000 feet, I have my carbs jetted as follows:

Left Carb - 280 main Jet, Powerjet - 140
Right Carb - 280 main Jet, Powerjet -145

Now, this is still just a tad bit rich from my plug readings, but the power is fantastic. One other thing to note, is factory gear ratio's are roughly about 10% to high. A factory stock gear case was a 17/31, if I am correct, and I have mind geared down to 15/31. Granted I have given up about 9 to 10 MPH on top end, but the machine is an animal for hill climbing and in deep powder, corner to corner is awesome and I can keep up with most 700's and a few stock 800's, besides this, I'm to old to going much over 80 to 85 MPH anyway, it scares the hell out of me!