Low end issues on 92 yamaha venture - Snowmobile Forum: Your #1 Snowmobile Forum

jdr1813 · 02-24-2008, 05:30 PM

Have a 92 yamaha venture. Have always had very poor performance on trails and anything low end. This goes way back for many years. Each year i try something different.
Have changed plugs & wires, coil, CDL box, used set of carburators, drained gas tank, drained oil tank, differnet oil, different gas, Carbs cleaned over a dozen times, and this year new boyson reeds, main jets, and pilot jets and floats set... I have tried adjusting the air screws two. NOTHING WORKS.

It is boggy on the low end. Especially after going through the trails. Get her on the high side and she runs like a champ. Sometimes it gets so bad it will just stall out on idle. It appears like the engine is getting hot(all vents are open). The hotter it seems to get, the worse it runs. The the hotter it gets it starts to make a gurggeling noise. Not a pinging noise (as in detonation) but a gurggle noise. I live in Michgan at 750 elevation. Riding Temps are usually 20 to 30 degrees.

I was going to knock the main jet down 1 size, but my problem is on the low end circuit. Any suggestions out there??

**RJ Gleason** · 02-24-2008, 06:00 PM

Gurgling usually means that it is boiling the gas unless it is a L/C engine in which case, there is probably air in the cooling lines.
Is it a Fan cooled or Liquid cooled?

jdr1813 · 02-24-2008, 06:04 PM

It is air cooled. It is a 485cc engine. I believe it would be the same engine that a phazer has

**RJ Gleason** · 02-24-2008, 06:18 PM

Did you take the engine shroud off and check for a mouse house in there?

jdr1813 · 02-24-2008, 06:30 PM

Oh yeah,
Actually I didn't write this, but over the course of 10 years it has been to 3 different dealers. One dealer had the engine right out (at my request) as I was looking for any kind of chaffed wires. No luck there either.
What about this boiling gas? Where in the engine does this occure? Carbs? Inside engine? Where abouts would this be taking place?
Here are things I have not done.
Check timing (don't know how)
Fuel Pump
Oil Pump
Replace fan blower belt.
If this is a cooling issue, what makes a snowmobile run hot if the outside air temp is at 25? I know bad timing will make heat.
Any advice on plugs? Can I run a cooler plug? Current plug is BR9ES
I see no way to tighten the cooling fan belt. Maybe that thing is slipping.
Any idea what the temps should be? I could try a thermometer in there to see what it runs at, but I don't know what "too hot" is.

**RJ Gleason** · 02-24-2008, 06:36 PM

If the gas is boiling, it's way too hot.
The gas will boil in the carb and could cause vapor lock.
Check under the engine shroud for any blockage. (mouse house)

jdr1813 · 02-24-2008, 07:13 PM

I couldn't take it so I run out to the shed to take a look.
Looking through the spark plug holes and looking in at each end, I see nothing. No grass twings or sticks. But I will pull the shroud.
Keep thinking old cat rider. Your thought is good one, but i think i won't be that lucky.

dkarwh · 02-24-2008, 09:43 PM

I would check the belt tension with it cold and see if the belt is loose. If I remember correctly the belt is adjusted with shims, take out shims and the belt gets tighter, put in shims and it gets looser. My friend had a phazer that did the same thing. After I adjusted the belt no more problem.

**RJ Gleason** · 02-25-2008, 01:50 AM

Best to eliminate the easy/cheap fixes first.

jdr1813 · 03-05-2008, 07:03 PM

I always check the belt tension and it seemed good.
But I took it apart looking for the shims. Oh boy. Pulleys are not good. Top one has a nice deep groove wore in it from what has to be slippage. I bought a new belt, but now I am going to buy new pully. I am thinking this may be the problem with the poor running.
Now, since this has went on for several years what I have I done to the motor?