Snowmobile Fanatics banner

1 - 19 of 19 Posts

·
Registered
Joined
·
193 Posts
Discussion Starter #1
well, back a few weeks ago i started my sled (the carbs were drained over the summer..stored indoors) and it would not start on its own, but if i blew into the vent lines on the carbs, i could hear this bubbling sound and the sled would fire right away...only thing was it would rev right up to clutch engagement and start to pull away....So once it warmed up the idle died down a bit, bla bla...took it for a ride and it just fell on its face..no power, no nothing. One plug was white (overheated)...I thought I had cooked my engine, but thankfully it was a faulty compression tester!!..I have OK compression both sides . I took off the carbs, blew out all the passages with compressed air & carb cleaner (but the carb was clean...not a spec of dirt anywhere because it was drained...I cleaned it out anyway) Checked the carb boots for cracks, put the carbs on and installed the airbox. Same thing....it will fire up but rev really high and I have to jog the kill switch. I replaced all the fuel lines and the pulser line, the gas flow from the fuel pump was pretty good (primed right up when i pulled it over a few times)....What am i missing, this thing ran primo last summer? how high are the slides supposed to be at closed throttle? Mine are about 1/2 to 3/4 inch..they are synced....I'm lost!!
 

·
Registered
Joined
·
8 Posts
As a starting point, have you pulled the pilot and main jets out of the carbs? The pilot holes are very small and are prone to plugging. Given the small diameter, you may just want to pick up a couple of new pilot jets and plan to replace them once pulled.

Regarding the slides, I'm not sure about your exact carb setup, but 1/2" to 3/4" sounds like way too much gap. Find a gage pin (or drill bit) around .200" dia and start there.

FWIW, the only time I ever stored a snowmobile by draining the carbs and made sure ALL the fuel was out, I had plugged pilots at the start of the next season. Since then (the last 25 years) I've only stabilized the fuel and fogged the engine before storage, and have not had a even a hint of an issue at the start of the next season. I know storage technique is a highly personal matter, but this has worked for me, and it doesn't get much easier than what I'm doing now.
 

·
Registered
Joined
·
5,400 Posts
Also, the crank seals need to be checked if the carbs and boots are not the problem.
 

·
Registered
Joined
·
841 Posts
Is this your Indy 400?

For the slides, there should only be a small gap on the bottom. Each engine is different but 1/4" sounds like a lot.
Are the slides stopping when they hit the idle screw or are they hanging on the cables? Back the screw all the way out and see if the slides drop.
Are the slides installed properly?

If there was any small amounts of fuel left in the carbs, it is very easy for it to dry up and leave a fine dust or crud. This is not dirt from the outside, but what's leftover from dried up fuel. I have seen pilots plugged right off because of that.
When cleaning the carbs, you must remove all the jets, pilots and then clean the passages.
 

·
Registered
Joined
·
193 Posts
Discussion Starter #7
well, I can only lower one slide down, the other carb is screwed right down as far as it can go?? so it looks like I cant lower them any more. I took it for a 5 minute boot just now, and it ran good, but with the choke off and warmed up the idle still races up way too high (4000k) The plugs were good...one seemed wetter than the other but both dark and not white....can i richen up the idle a little?
 

·
Registered
Joined
·
295 Posts
All the suggestions are good so I will add one more
Reeds? what shape are they in? (if it has any)
As for the carbs with an engine over 2000 miles I have always replaced the needle and seats as well as the pilots
As far as your throttle fully closed about a 1/4 inch is pretty close
but if only one carb will drop that far I would almost think about swapping the carbs around
Im thinking made a cable too tight or no freeplay in the cable
 

·
Registered
Joined
·
193 Posts
Discussion Starter #9
the cable is not pulled tight....i just set the mixture screw bang on 1.5 turns..still high idle. sprayed wd40 around the carb boots and base gasket...doesn't seem to change the idle....is there another way to adjust the idle other than lowering the slides?
 

·
Registered
Joined
·
193 Posts
Discussion Starter #10
well, the high idle is still there...but it seems to run good...smooth and powerful at all rpm's....no misses or backfiring. What should the plugs look like? they are not white after a 10 minute ride.. but they are a "dry" chalky brown and it looks as if the insulator below the electrode has blistered (but again,its not white its brown) there is an oily build up to the base of the plug, but the electrodes are dry and brown (I'm used to seeing a bit wet...)
 

·
Registered
Joined
·
1,109 Posts
Try turning the air screw in 1/2 turn and see if it'll come down from High Rpm's. If it comes down a little, maybe another 1/4 turn, and try again. Keep doing this until you reach the desired idle. This is if all other things are correct. I started my last rebuild and was getting about 4k rpm's with everything tuned properly, then I turned in the air screws 1 full turn in, I started at 1.5 out. Idle came down nicely.

3/16" to 1/4" gap on the carb slides. Just make sure they both open at the same time and fully open. Check by running your finger in each carb with holding the throttle....not while it's running either!
D
 

·
Registered
Joined
·
193 Posts
Discussion Starter #12
yeah..they both open at the same time...and i think I'm a little higher than 1/4 inch on the slides...but i cant drop down any lower. Ill tinker a bit with the air screw just have to keep checking the plugs for signs of overheating
 

·
Registered
Joined
·
1,109 Posts
If there are no air leaks and everything seems to be correct...got me thinking. Is the throttle cable seated corrected behind the thumb throttle? That may hold it up a tad. And is that the stock cable that came with the sled originally?
Just trying to rule out simple fixes.
D
 

·
Registered
Joined
·
193 Posts
Discussion Starter #14
yep...its the cable I had on it all last season. I did check the throttle but I'm gonna re-check that...because it just doesn't make any sense that the slides are higher than last season [xx(]
 

·
Registered
Joined
·
1,109 Posts
I was thinking last night about this on my way home.
Did you take the cables out of the slides and remove the cables completely from the carbs? If so, are they put back together correctly? There are 2 nubbins (don't know what to call them) of the end of the cable. The lower one is larger. The larger once should be the one that is slid into the slide, and moved into the grove, then the plate should rotated to secure it in the groove. That smaller nubbin remain on top, not in the groove. You should be able to see that one (smaller nubbin) without removing the cable. The distance between the 2 nubbs is about 1/4".
Just still trying to help.
 

·
Registered
Joined
·
8 Posts
Racing666 has the right idea, and you can carry it a step further by unhooking the slides/needles and gently lower them back into the carbs to be sure they both seat all the way down. This would at least eliminate any issues with the cables should they drop all the way in. A bent needle, or an obstruction in the needle jet or slide cavity, could prevent the slides from dropping all the way down.
 

·
Registered
Joined
·
502 Posts
check what Dman said too.. i have put my carbs back together wrong when i was a noob.. i didn't realize there was a notch in the slide wall that had to be lined up with the valley on the round slide. i put it together with the notch 180 degrees from where it should have been, so when i started the sled, it took off on me and crashed into the back wall of my garage lol..
 

·
Registered
Joined
·
193 Posts
Discussion Starter #19
hahaha....your just lucky it hit a wall and didn't have a hole yard to pick up speed before crashing into a neighbors car! [:D]

The air screw suggestion seemed to work..I turned them in about 3/4 turn each and the idle settled down and it seems to run good. Thanks for all the suggestions....this sled is for sale as well if anybody is interested. Pretty good shape for the year (1987 indy 400 liquid)...could use a new seat but overall its a good sled... price will be under $1000
 
1 - 19 of 19 Posts
Top