78 Intriguer 440 engine with a 79 340 drifter carb

[whitley1983]

Ok, so my father in law picked up a 1979 340 Drifter and a 1978 440 Intriguer. He put the motor from the 78 Intriguer in the 79 Drifter. He was missing the airbox on the intriguer and a local snowmobile mechanic he knew said the carb off the 79 Drifter would work fine with the 78 Intriguer motor so he did that because the Intriguer carb wouldn't fit into the 79 Drifter airbox. We got it running the other day and at first it backfired out of the airbox a few times but then ran great in the garage with the track lifted up but then when I went to run it down the road it bogged down and didn't run good. He took it to his mechanic friend and he replaced the jets on it but it's still not running as good as it should. Looking through the service manuals I have found that the 1978 Intriguer carb is a Mikuni VM 34 Zinc and the 1979 340 Drifter is a VM 32 Econo Jet, the Intriguer 440 has a 270 main jet and the 1979 340 has a 230 main jet. I'm not sure what main jet that guy put in it, but my question to you all is whether or not you think that carb from the 79 drifter will work well with the 78 intriguer if the main jet is changed to match the engine or if other parts of the carb need to be replaced? For reference the 79 drifters had the same carbs for both the 340 and 440, they just had different main jets, air jet, jet needle, and needle jet.

[Checkmarks]

Lots of tough questions.

Sure a smaller carburetor will work.  The main jet the one the mechanic changed, may or may not be correct.  Keep in mind we are only talking about "wide open throttle (WOT)".   This WOT is completely controlled by the main jet (not perfectly but close enough); if you  operate your throttle in two positions idle and WOT. With the proper main jet and only using WOT and idle positions the sled can run without burning down.  The other throttle positions are Dangerous if you're not running rich.  Running lean will cause the Pistons to melt/vaporizer and go out your exhaust pipe.

Best solution is to make the bigger carburetor work in the airbox.  Dremel the hole bigger.  Make it fit. 

[Interceptor398]

Do we know the condition of the seals in this motor?

[whitley1983]

He replaced the seals, the engine has equal compression at about 175 per cylinder which we checked with multiple gauges. Turns out that mechanic changed all the jets in it not just the main jet, it def runs better and doesn’t back fire but it still doesn’t seem to be running as good as it should. I looked at the service manuals for the intriguer and the drifter and I can’t find any differences in the specs between those two motors but obviously they paired that carb with that motor for a reason. I’m trying to convince him to just get that carb and air box that way there’s no guesswork involved.

[Interceptor398]

If you had the original carb on the Intriguer it would be marked 34/179-  main jet = 270 and a 20 pilot jet.

The 79 340 Drifter carb would be marked 32/143  and have 230 main jet with a 25 pilot jet +a 110 round reverse type power jet.

The 79 440 Drifter carb would be marked 32/142 and have a 260 main jet with a 25 pilot jet + a 120 round reverse type power jet.

Not sure if this helps??

[whitley1983]

If you had the original carb on the Intriguer it would be marked 34/179-  main jet = 270 and a 20 pilot jet.

The 79 340 Drifter carb would be marked 32/143  and have 230 main jet with a 25 pilot jet +a 110 round reverse type power jet.

The 79 440 Drifter carb would be marked 32/142 and have a 260 main jet with a 25 pilot jet + a 120 round reverse type power jet.

Not sure if this helps??

Hey man thanks for the info, I had found the different jetting specs in the manuals online but my main question was if you could use the VM 32/143 carb off the 1979 340 drifter on the 78 440 Intriguer motor if we replaced the jets in the VM 32/143 to match the spec for the jets in the VM 34/179 or is the fact that they are different bore sizes a big enough difference to not be able to use it at all and expect good performance? As Checkmarks stated he said that using a smaller carb is dangerous as I'm assuming the change in bore size changes the air/fuel ratio potentially causing the machine to run more lean? I know there are adjustments on the needle to make it run either more rich or more lean so I'm not sure if using the smaller carb with the other jets would result in a need to move that clip up or down? I just don't know enough about how the carbs work and what the effect is of using a smaller bore carb results in? Like I said before I'm trying to convince him to track down a VM 34/179 carb and just use that but he's kinda hard headed.

[Interceptor398]

I would think that a VM34 carb could be jetted to you needs, there are a lot of 440 drifters out there to get a carb from.

[Checkmarks]

When you play with/ swap parts from the airbox to the end of the exhaust pipe the engine runs with different A/F (air fuel) requirements.  The published information you can get at online is for only that sled!  Dangerous was a poor choice of words on my behalf maybe better "a poor choice".

Yes the bore of the carburetor changes everything, literally.

Your 440 is designed for a 34mm carb with purpose.  Putting the 32mm carb will choke the horsepower and there is not much to play with to start.  Even if you do tune like a master mechanic the motor will be down in Hp (no bueno).

It is from my early work and experiences putting holes in Pistons, gouging cylinder walls, and breaking motors I share with you.  How much is the sled worth running and the multiply by 0 when you melt the motor.