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Popping Puma

3K views 18 replies 3 participants last post by  kccats 
#1 ·
This has come up the last two times I rode the Puma. It's been a bit finicky to start cold. Takes a bunch of pulls, will back fire, then takes some time at the throttle to keep it running. Once it's been ridden for a bit, it'll idle and restart no issue. After sitting for an hour or so, a bit hard to start and needs some throttle to stay running. Adjusting the idle on the carb has helped, but that's more of a bandaid.

When I let off the gas while riding at lower speeds, I get a popping noise. Almost like it's engine braking.

I rebuilt the carb last week...full teardown and clean. Pilot jet was clean...but I soaked it and cleaned it with wire anyways. Air screw was out 3/4 of a turn; backed it out to 1 turn per the service manual. No change in the above.
 
#6 ·
No one does! But at about 10 years old if I go into it I would put seals as well as pistons!
Just so you have an idea, the pistons are about $40 ea and the gasket set with seals is about $25!
So you can freshen the motor for about $200 with shipping!
 
#7 ·
Wondering if I should do both this off season. Jag is the same age and has about the same miles. What's the easiest way to check the pistons? Pull the exhaust manifold? The Jag runs well. But I'm not sure if it's ever been rebuilt or not.
 
#9 · (Edited)
120 on both cylinders. It started in two pulls, needed a little throttle attention but ran great once warmed up; no popping. It was in the 40's for temps. Not sure if that had anything to do with it? It was just around freezing when I did the compression test two days later.
 
#15 ·
I'm stumped on this one. No popping this weekend riding around on the trails; only pops before it's up to temp. Both sleds actually do that.

This machine takes a number of pulls to start when cold. You can't let it idle on it's own. You have to sit there and hold the throttle to keep it from stalling. I've tried adjusting the idle speed, but that doesn't help. Just ends up idling too high once it's warm. Fires right up when warm. But let it sit for a bit, and you have to give it a little throttle when pulling it over to get it to light off. So almost sounds rich? Maybe a choke plunger issue? I've been through the carb..it's spotless. Air screw is 1 turn out.
 
#16 ·
Is the choke closing all the way?

Make sure the choke plunger is actually hitting bottom.
 
#17 ·
I would still at least go threw the carb and all the passages as well as the jets!
Also check the float 'Level'?
Have you done a compression test cold with throttle wide open and then again when warm?
Then yet again with a few drops of oil in each hole?
 
#18 ·
I pulled the carb and rebuilt it last month. Everything is good and clean. Compression when cold is 120 each side. I haven't done a compression test when warm yet.

I really need to check the choke plunger....
 
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