Snowmobile Forum banner

1 - 20 of 33 Posts

·
Registered
Joined
·
7 Posts
Discussion Starter #1
I have a 92 yamaha 480 that is bored .20 over ( I got it that way) that has a habit of burning a piston.To hopefully get it to run richer I made the change to the carb, replacing the primary nozzel with the 3 and putting the additional hole in the secondary. It starts and idles fine but bogs and will not rev up. cleaned the carbs and jets many times, went back to the standard main nozzels nothing seems to make any difference. I have good spark but is it possible that one cyclinder is dropping out when throttle is applied? Any ideas of where to go from here?
 

·
Premium Member
Joined
·
34,103 Posts
Have you tested for air leaks?
Usually burning a piston is due to not enough fuel, or too much air.
Is that piston the PTO side?
check the crank seals.
 

·
Registered
Joined
·
7 Posts
Discussion Starter #3
burnt piston was on the PTO side. Assumed because of the engine modification, it was lean in the mid range. Thats why I did the changes to the carb.
 

·
Registered
Joined
·
50 Posts
Had the same problem with my phaser (it's an 88) Mine stoped after i reset the float levels and replaced the fuel lines from the fuel pump to the carbs. Though i'm sure it didn't hurt having the float levels right, i think the main problem was the fuel lines were too short, causing them to kink and not letting fuel flow enough.
 

·
Registered
Joined
·
7 Posts
Discussion Starter #5
I had to take a break but i'm back. I set the floats, changed fuel lines, checked the reeds, cleaned the carbs again, new plug caps,new spark plugs, still bogs won't rev up when throttle is applied. It starts on the first pull. When idling I pulled the pto plug wire and it sounds the same (bogging) Spark plug in that wire shows strong spark. I did the same to the other side and got the same results, bogging, good spark. It will start with either plug wire disconnected. 110 psi on compression test both cylinders. I'm at a loss of where to go from here
 

·
Registered
Joined
·
50 Posts
Probably a silly question, but does the track turn okay? I accidently had my brake locked the other day and it made it seem as if it was boging down when i hit the throttle.
 

·
Registered
Joined
·
7 Posts
Discussion Starter #8
Ok all you yamaha wrenchers, I am about to make a swimming raft anchor with this machine. Does anyone out there have any ideas on what is causing this problem? All ideas and suggestions welcome and appreciated.
 

·
Registered
Joined
·
94 Posts
does that model sled have a throtle safty switch ? ( 2 wires going to the carb) if it does un plug it at the carb and conect the wires from the harness together to complete the circut ... try that
 

·
Registered
Joined
·
7 Posts
Discussion Starter #11
I have good flow from the fuel pump. This engine does not have a throttle safty switch. Thanks for the input keep them coming.
 

·
Registered
Joined
·
315 Posts
do you have another phazer? what i am suggesting is that maybe the coil is firing when you pull the wire off and set it there,but is it firing under load? i have seen them do that before .
oh ya another thing is the wire end (the cap that goes right on the spark plug ) it is removable and it is possible that it could be giving you a problem . the wire it self could be green where the spark plug end and the wire connect ,check that and make sure that is not your problem ??? you could do an ohm test on the coil if you didnt have another coil to see if it is within spec .
when you did the carbs did you make sure the plugs in the bottom are in the proper location?
 

·
Registered
Joined
·
75 Posts
i had that problem not too long ago, turned out the pulse line had a crack right at the connector on the engine
 

·
Premium Member
Joined
·
5,737 Posts
have you properly set the air screws? when you cleaned the carbs did you pull the choke plungers and confirm clear passage? does it bog only with the trottle lever in a certain position like at or below 1/4 throttle? or is it bogging only when you pin the throttle?
 

·
Registered
Joined
·
63 Posts
Have you tried NEW plugs? Ive had many concerns with ngk plugs . (Spark looks good but under compression and fuel they foul) What happens when you artificially add fuel? (spray fuel into carbs). Plugged exhaust?
 

·
Registered
Joined
·
7 Posts
Discussion Starter #16
I have changed the spark plug caps with new. choke passages are clear, plugs in carb are right, adding starting fluid directly in carbs doesn't help and will almost kill the engine. Exhaust is clear, adjusting air screws makes no difference, bogs at all throttle positions will not rev, coil ohmed out but will check again, new line on pulse but will check and redo
 

·
Registered
Joined
·
20 Posts
i had a phazer and i had to have the choke on the whole time. dink with your choke once. idk just throwing that out there for ya. there good sleds. i hope you get it running i loved my phazer...but she burned up last winter :(
 

·
Registered
Joined
·
63 Posts
I had an ovation with a bog issue. Not sure what cured it. I installed a ground wire from coil to engine block plus a lot of other stuff.( plugs,ALL new hoses,redid plug boots on wires...etc..) but dont know one which fixed it. Sounds like you did all of them, minus the ground... worth a try?
 

·
Premium Member
Joined
·
5,737 Posts
is it bogging under load? meaning is the track on the ground with you on it? or do you have it on a stand and its bogging? i see in a previous post where you didnt have the belt on. has the belt since been installed?
 

·
Registered
Joined
·
245 Posts
One other thing you may check. How do the plugs look? Its possible that the injector cable is not set properly, so when you give it gas its injecting too much oil which is causing it to bog. You may look at were the cable screws into the carb/throttle mount on the carb. Just a thought!
 
1 - 20 of 33 Posts
Top