need help-- '90 inviter bogs off idle

Millinocket Rocket

Millinocket Rocket

New member
Joined
Mar 25, 2005
Messages
725
Age
57
Location
Sebago Lake, Maine
i've got a 90 inviter with a keihin carb, and it's got a serious low end bog off idle. it's bad enough to stall the machine out. it only has 800 orig. miles on it. bought it for my son and when we first got it, the bog wasn't as bad-- it's gotten progressively worse. now it's like you turned the key off till it gets past the bog. i took the carb apart(looked really clean) and cleaned it good (twice) with carb cleaner and blew it out with compressed air-- pilot, main jet, needle & seat, air jet, fuel screw etc. put it back together and it didn't get any better. tried turning fuel screws out-- no better, but, when it's bogging and just about to stall, if i feed it a little choke it comes right to life. was going to try going up a size on pilot jet, but not sure if that's the problem-- don't understand how a pilot jet becomes progresively worse? the stock jet says 50 on it.. anyone know the next size up-- or any other suggestions?? thanks for any input :o|

also tried bypassing tors with no luck
 

I am not familiar with those carbs, but you said you turned the fuel screws out and it is no better. Are you sure they are fuel screws and not air screws? If they are air screws then they need to be turned in to richen it up. If you rev slowly will it engage? When does it bog, before engagement or as it is starting to engage? If it bogs on engagement then you might need some new clutch springs. If they have never been replaced they could be sacked. Is the belt worn?
 
thanks for the replies--
daman-- i think it's getting enough fuel, i took the fuel line off and fired it up--gas came pumping out. if i feather the throttle through the bog (and it doesn't stall out), it takes right off and runs great.
watchmaker--you are right- they are air screws-the tune up sticker on the clutch cover says-- air/pilot screw 1-1/8 turns out, so i tried turning it in and it just about dies. the clutches should be all set-- i just put new springs in both and cleaned them up. one other thing is there's a welch plug on the top of the carb-- wasn't sure if i was supposed to take that out and clean inside there or not? any other suggestions?
 
I'm not familar with that carb but maybe a bigger pilot and or raise the needle if equipped???

by your description it's not getting enough fuel somhow...
 
Millinocket Rocket said:
ya, that was my thought too, i guess i'll try a bigger pilot-- not sure if it's got a needle, it's a butterfly carb,. thanks
Click to expand...
Ok, no on the needle then...
 
This probably isn't whats wrong with your sled, but mine was bogging off idle 'cause the motor mount was broke. This caused the engine to twist in the chassis, which caused the belt to ride higher in the clutch.
 
Jeffro said:
This probably isn't whats wrong with your sled, but mine was bogging off idle 'cause the motor mount was broke. This caused the engine to twist in the chassis, which caused the belt to ride higher in the clutch.
Click to expand...

thanks -- i'll check that out too
 
well, i tried a new pilot jet the next size up from stock and it didn't help. still got a bad bog. idles fine and revs good once you get past the bog- if it doesn't stall out, and like i said before-- if you touch the choke while it's bogging, it snaps right out of it. any other suggestions?? thanks
 
take the primary apart. it might be gunked up so nothing is pivoting properly. throw a new spring in there while you are at it cause that one is probably weak.
 
maim-- thanks for the reply, the primary is like new- the sled only has 800 orig. miles on it. i just cleaned it and put a new primary spring in it just to make sure the old one wasn't sacked. i think it's definitely a motor/carb issue. if you stab the throttle from idle it will die if you don't feather it to keep it alive- or give 'er a little choke. maybe i'm missing something in my carb cleaning. i've got carb cleaner to come through every hole in this damn carb. the only thing i haven't cleaned yet is to pull out a welch plug on top of the carb. i wouldn't think it would be a float level prob or fuel pump prob where it's just like a dead spot off idle and runs fine mid and top and idles fine.
 
how did the ventiri tube look above the main jet? couple of the holes might be plugged if it is removeable.
 
hello,
another idea to check, if the sled is 18 years old and only 800 miles, it must have been in storage, which if long enough, can dry out the crankshaft seals, making them leak and therefore not having enough vaccum to operate the fuel pump properly. next time you fire it up, spray some brake cleaner or something behind the clutch at the seal, and if you can get to it, also do the mag side. if your engine speed goes up or down, you know it's whats wrong.

Good luck,
Russ
 
well, the main jet and its tube looks very clean to me, i can spray carb cleaner right up through the hole and see through it no prob....
also tried spraying starting fluid at the crank seals, carb boot areas, etc. and no change in rpms.
compression is over 125.
i also tried running a fuel line from a gas can to the fuel pump to rule out the filter in the tank- which i took out and looked fine.
put a new fuel line on between the pump and carb, new oil line between oil pump and carb to make sure that wasn't sucking air, checked the fuel pump out, nothing wrong with it.
i'm pretty stumped. i wish i could move on to electrical but i know it's got to be fuel related because of the choke bringing it out of it when it's bogging.
the float height is supposed to be 15mm, so i took the bowl off, turned the carb upside down, measured from the bottom (now on top)of the float to the carb body, and it was exactly 15mm.
oh well, i've got plenty of time to research it before next season! any more advice is welcome
 
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