Polaris ATV Forum banner

1 - 8 of 8 Posts

·
Registered
Joined
·
24 Posts
Discussion Starter #1
Okay...long story, but bear with me:

I don't typically work on 4-stroke quads...actually I try to stick strictly to street bikes and smokers. But a machinest friend of mine whose made many parts for me without charging me needed some help so I took on the bike.

What he got was an '05 Predator with an Edelbrock carburetor setup. He didn't like the Edelbrock because it didn't have a choke and was hard to start. He bought a brand new carburetor from Polaris and installed it but couldn't get it to work.

What I'm looking at was no throttle cable (fixed), and a fueling issue. Biggest concern here is that he's been trying to start it with the fuel hooked up incorrectly. There is a 1/4" nipple just above the bowl on the left side of the carburetor that was left open. The fuel line was hooked up to a large 1/2" nipple on the side of slide barrel...I usually see this connected to the air box and it tends to operate the neddle slide with vacuum on other bikes. I don't believe this is correct but haven't been able to confirm...I think the fuel delivery should be at the 1/4" nipple.

I've tried drying the carburetor and blowing all the fuel out of the cylinder to dry it. Then I poured fuel into the bellmouth to prime it. Any other bike, except those with bad compression, at least fire under this treatment. This one does not.

I have not checked compression, but it does seem weak to me (placed my hand over the bellmouth and there just wasn't much pull when cranking). I do know that there is adequate spark.

Any suggestions would be greatly appreciated.
 

·
Premium Member
Joined
·
20,001 Posts
First off, welcome to the board!
 

·
Registered
Joined
·
24 Posts
Discussion Starter #3
Thanks.

Compression was definitely low. Read 50psi cold. Compression can be messed with by poorly adjusted valves but the exhaust was spot on. The intake was a little tight at .00419", but was still within the tolerable range (.006 +/-.00191). It's my understanding compression should be around 125psi.
 

·
Registered
Joined
·
4 Posts
Yes the compression is WAY too low, unafortunatly I don't know what the exact #s. Mine was in the 100's be-fore the rebuild. These bikes fuel don't operate on gravity flow tho, might be somthing of that nature. the fuel (pump) is located on the front below the bars. They can clog up and quit working (flowing) if set-up for a while.

Goodluck and let us know what it is when you find out.
 

·
Registered
Joined
·
24 Posts
Discussion Starter #5
Can you tell me if the cylinders are nicklesil coated? That in itself cost $250~300 to repair from my local machinist and I'd like to let me customer know before we get into it.
 

·
Registered
Joined
·
4 Posts
You know I don't really know that...sorry. My machinist didn't say anything about it at the time so I dunno.
 

·
Registered
Joined
·
24 Posts
Discussion Starter #7
The cylinders are nickle plated. I was also able to get this bike up and going after getting the jug swapped out. Wha thad happened was the way the fuel had been connected had just dumped gas into the cylinder, which washed it out. The rings and bore were shot.

Just posting in case somoene searches along with similar symptoms. That was my own resolution.
 

·
Registered
Joined
·
39 Posts
Just a suggestion if your going to dump 250-300 on a top end rebuild it might be worth it to go a step further and get a 540 bbk there like $500 for the kit unless you already have it.
 
1 - 8 of 8 Posts
Top