[ExciterRob]

This weekend, I finally got to some snow and was able to have my son put some miles on his 88 Exciter. Every thing was fine until about 5 miles in to the ride. We went to leave the stop sign and his sled would barely move. I pulled the plugs and they were black and oily. I ran the starter for 15 seconds or so with the plugs out, then reinstalled them. It then started right up but I couldn't get more than 4k out of it for the first 1/4 mile. Then all of the sudden it came under "normal" power and to off. I had my son open it up at every corner, but it happened again within 5 miles. Changed the plugs... again it failed. Compression is 120 and 117 pto and magneto respectively. Running BR9ES plugs, using yamalube oil. oil injector cable has .95" of free play. PLEASE HELP!:dunno:

 

[RJ Gleason]

Is the choke closing properly?

 

[ExciterRob]

Just thought about that after I made the post RJ. I will have to check that tomorrow. Also I did jumper out the T.O.R.S. just to eliminate that variable.

 

[Phazer36]

Wow just yesterday I had the same issue. I really am having my doubts about NGK spark plugs. I just put new ones in my phazer, and it would start but run like crap. Similar to what you are experiencing. Just for the heck of it I put in an old set of plugs I had previously removed, and the sled runs sweet. Go figure!??? If you keep your old plugs, I'd try it, can't hurt. Seems like once NGK's get fouled or over oily they are shot.

 

[Phaze]

I've have only used NGK's for years. Check the gap and the insulator for a crack. From what I've read on other threads, could it be the clutch? Dirty/sticking?

 

[yamadad4]

couple things to check if it appears to be over-oiling. besides the already mentioned choke plunger. your freeplay on the cable sounds excessive but that would in theory make for less oiling. without me dragging the book out, check the oil pump for minimum and maximum pump stroke, if you have the info available. the oem cables used to have a dot stamped on them used for alignment more so than freepaly, but after the cables stretched a bit this became null. also, throttle habits and idling habits can factor in. if your rider is not using a wider range of throttle motion and more so holding a pattern, these sleds will oil up. went through it with my kids and taught them to blip the throttle more to clean out the sled. from a parental aspect it can be a bit overwhelming when your kid grabs a handful, but once the control is obtained by the child and parameters are set by the parent, the mechanical issues seem to fade. at least for my kids and i.

 

[ExciterRob]

RJ AND Yamadad, I tried to start the sled cold with no choke tonight. It fired like it ran on one cyl. I shut it off and disconnected the mag side plug wire and tried to start it and it ran like it was on one cyl again. Then I reconnected the mag and disconnected the pto... NO START. So I checked the choke freeplay on the pto side carb and found it to be none.. Had to increase the freeplay by 5/16" to get spec'd setting. Mag side required 1/8" increase of freeplay. Let it warm up and took it for a spin. Much more responsive, still hesitant. Maybe still a lot of oil/fuel in the engine that needs to burn out? Went through 2/3 tank of fuel and 1/2 tank of oil in 22 miles on sat. The freeplay on the oil cable was spec'd at .91" to .98", set at .95" with micrometer. ('93 sx Motor). Will try to blow out tomorrow if we still have snow. Anything else I should check? BTW, the plugs are now dark cocoa brown and dry.

 

[yamadad4]

check the choke cable itself, the two into one will sometimes hang or only pull one side. that plastic coupler thingy is where you want to look. had to replace one of the cables on my 93 sx. i also had alot of issues with the needles and seats on that sled if your running the flat slides that came with that motor. not that i would recommend it to all, but i occasionally ran the br8es plugs in that sled in temps above 30 when my kids rode it for the same issues: plug fouling. try it at your own risk, just avoid extended wide open pulls. this worked when my then 8 yr old daughter was riding that sled. fuel usage sounds a bit high for the mileage and oil sounds excessive. assuming your running the 88 tanks, the fuel would have had about an 8 gal capacity and the oil around 3 qts, as most the yamahas did until 97. so, 6 gal or less divided by 1 1/2qts would throw your ratio at around 16:1, give or take. should be up around 40 or 50:1

 

[ExciterRob]

I was wondering about a hotter plug to help with fouling. Unfortunately, I won't be able to test the adjustments fully for a while as it started raining this evening and the forcast calls for thunderstorms tomorrow. Since we can't ride, I picked up a project sled tonight to keep me busy for a couple days. It's a '90 A/C Prowler with bad drive bearings and poor idle. I wonder if the carbs are dirty?:laugh: Thanks for the input, I will keep you updated.

 

[ExciterRob]

Ok, so we finally got snow to ride on this weekend! I took the Exciter out for some test passes and here's where it stands. After pulling and cleaniing the carbs for the second time, it is idling perfectly at 1800 rpm's. At wide open throttle, it seems to be firing and running as it should. But at 4-6k, it will run and begin to lose speed like it is only running on one cylinder. The pto side plug seems to be slightly lighter in color than the other side, but both sides of the head seem to feel the same temperature wise. Could it be a faulty decompression valve? I have tested the primary and secondary side of the coil and both are within specs, as well as the spark plug wire caps. I am at wit's end with this thing. Any further help would be appreciated!

 

[Yamaha440]

Wow just yesterday I had the same issue. I really am having my doubts about NGK spark plugs. I just put new ones in my phazer, and it would start but run like crap. Similar to what you are experiencing. Just for the heck of it I put in an old set of plugs I had previously removed, and the sled runs sweet. Go figure!??? If you keep your old plugs, I'd try it, can't hurt. Seems like once NGK's get fouled or over oily they are shot.

Hey Phazer36, do you gap the plugs?

Also, I've found a sandblaster will rejuvenate used/ fouled plugs.

 

[yamadad4]

i really dont think the decompression valve has that much effect. you could actually delete it if you wanted to.

when you tested the coils, had the chance to cool off or did you test right after?

on the plug caps, heat wont be an issue but vibration will. if you test them on the bench they can read ok. now wiggle the snot out of them and test again, or test while wiggling. compare the readings.

i am having a tough descision between electrical and fuel. hows the ground strap look on the coil? any deviation in the wire itself along its path? like its occasionally loosing connection?

do your carbs have that power jet affair or was that the previous year?

 

[ExciterRob]

i really dont think the decompression valve has that much effect. you could actually delete it if you wanted to.

when you tested the coils, had the chance to cool off or did you test right after?

on the plug caps, heat wont be an issue but vibration will. if you test them on the bench they can read ok. now wiggle the snot out of them and test again, or test while wiggling. compare the readings.

i am having a tough descision between electrical and fuel. hows the ground strap look on the coil? any deviation in the wire itself along its path? like its occasionally loosing connection?

do your carbs have that power jet affair or was that the previous year?

The coil had been setting in my shop for 24 hours (45 degree's). The ends where the caps screw into where cracked a bit, so I cut them back to good cable and reattached the caps. As far as the power jet affair, I am not familiar with what your talking about. The only other thing I was thinking this could be is a weak fuel pump? Maybe it is strong enough for a good idle, and with the high amount of vacuum at wot, it again has enough pressure, but at mid range it lacks both enough pressure and vacuum to obtain a good running condition? Just grasping at straws at this point!

 

[yamadad4]

that would be a good one to grasp at. inexpensive and easy to change.

if the power jet didnt ring a bell, your sled is not equipped.

you did the right thing cutting back the wires. cant go wrong there.

hopefully your not loosing vacuum in the midrange due to a seal with a pinhole, hence the lighter colored plug on the clutch side. maybe another 1/4 turn one way or the other on the air screw would clean the color up a bit.

 

[ExciterRob]

that would be a good one to grasp at. inexpensive and easy to change.

if the power jet didnt ring a bell, your sled is not equipped.

you did the right thing cutting back the wires. cant go wrong there.

hopefully your not loosing vacuum in the midrange due to a seal with a pinhole, hence the lighter colored plug on the clutch side. maybe another 1/4 turn one way or the other on the air screw would clean the color up a bit.

I thought the air screw only adjusted the mixture through the pilot jet which controls the idle, not the mixture with the main jet. As for the seal, I think your referring to the pto and mag side crank seals. I can check those by starting it up and spraying some ether down by the seals, right? BTW, thanks again for your input.

 

[yamadad4]

yep on the seals. as for the carb adjustments, sometimes what its supposed to be isnt what it is. think outside the box.

wheres your needles set at? your crossing over from the low speed circuit to the high speed circuit and having an issue. if the pump is good, you need to help the transition between idle and main. float level, needle height, even the nozzles. it just gets more and more complex.

 

[ExciterRob]

yep on the seals. as for the carb adjustments, sometimes what its supposed to be isnt what it is. think outside the box.

wheres your needles set at? your crossing over from the low speed circuit to the high speed circuit and having an issue. if the pump is good, you need to help the transition between idle and main. float level, needle height, even the nozzles. it just gets more and more complex.

My air screws are out 1 1/4 turns right now. You would suggest to go out farther (richer) at this point? Also, should I adjust the idle speed up to 2-2.2k, (which would raise the needle height)? Sorry, hope I'm not being a paiin after all the help you have already given me!

 

[yamadad4]

no, your not being a pain, i dont mind helping at all.

where are the needles set at now? which slot is the e-clip in compared to the stock spec? at about twice the turns you should be on the screw(5/8 out sticks in my head for a starting point), perhaps you need to richen it a bit by raising the needles. not being condescending in anyway but the needles attached to the slides have slots in them and a clip to secure them. some have tiny little white plastic washers that like to disappear unexpectedly.

if you raise the needles, you add fuel. raise means the e clip will go in a lower slot. higher slot closer to the top of the slide, lower slot closer to the carb. hope that made sense.

its a simple adjustment, especially on the round slide carbs.

 

[ExciterRob]

no, your not being a pain, i dont mind helping at all.

where are the needles set at now? which slot is the e-clip in compared to the stock spec? at about twice the turns you should be on the screw(5/8 out sticks in my head for a starting point), perhaps you need to richen it a bit by raising the needles. not being condescending in anyway but the needles attached to the slides have slots in them and a clip to secure them. some have tiny little white plastic washers that like to disappear unexpectedly.

if you raise the needles, you add fuel. raise means the e clip will go in a lower slot. higher slot closer to the top of the slide, lower slot closer to the carb. hope that made sense.

its a simple adjustment, especially on the round slide carbs.

This has the radial flat slide carbs (93 sx Motor). I will look at the cd you sent me to look at the needle adjustments. I will turn those air screws in to 5/8 and see if I can get some positive results. Thanks for the help. I will test it tomorrow after work, assuming I don't have to wok overtime!

 

[yamadad4]

same principal, just a little more involvement to adjust. needles are dead center in the flat slides. remove the cover on top of the carbs, and you should see it. watch for the plastic shim washer.

its been awhile since i have worked on that style of carb. i dont think the linkage is in the way. i remember it being an easy pick with some needle nose or a hemostat.