Exhaust- Checked it, not clogged, tried to start w and w/out
Compression- low, I have compression tester
Piston in w arrow towards exhaust
Carb not completely closed and getting fuel
.002 Clearance is what Iwanted, BUT I after checking my ring gap after the bore and hone job there is no way it is even close to .002 with a ring end gap of .026-.027 . The guy who did it had to bore it to big which is why I am losing compression
Piston and rings match up with piston and ring size marked on them the same
Yes, have locating pins on the piston- can't mess that up
Ring end gaset at 28 where it should be, brand new
AND everything is sufficiently oiled, rings - cylinder, priorto installation and start

A professional would tell me low compresssion
Ring gap way to big .026-.027 (spec is supposed to be .009-.018)

 

You can check your own piston to cylinder wall clearence yourself with nothing more than a good feeler gauge set. Start with a clean piston (no rings on it) and a clean cylinder wall. Start with a minimum size thick feeler gauge like .001 and lay it against the Skirt of the piston. The gauge should lay against the full lenght of the piston and must be on the skirt side, as pistons are not round when cold. Then just insert it into the cylinder and push it all the way through the cylinder. Then repeat the proceedure with the next size larger feeler gauge until you can no longer push the piston all the way through.

The last size feeler gauge that would pass through will be your clearence.

The key to this is making sure the guage is against the skirt side of the piston and that things are clean.

Good luck.

 

Hi- everyone, havn't been on here in a while, but I thought I'd give you all an update. Still need some advice as well.

Well, had the motor rebored and honed by a different machinist company in town that is well respected. It costed a little more, but I had no problem paying it if it was done right. So, I put the new top end back together. It was hard to star but it finally started and ran good for the first few minutes until I gave it a little throttle. Then it held higher rpms and eventually started to increase rpms on its own and I had to shut it down. I confirmed the throttle wasn't sticking, so I am assuming air leak.

The next day I went to try and start the atv again. Again, it was hard starting, took a while, but once I got it started it ran great. I let it run for prabably 15 minutes then shut it down. Later I tried to start it again and took awhile to start again, but once it did start it ran fine. I let it run for about 20min this time. Both times I had it running it was on the trailer and It was only in neutral. I did this one more time that night.

The 3rd day it was a hard start again and it went back to the same symptoms as before with low rmps at first then reving. I figures mabe air leat at the intake boot region. But, I have tried spraying WD40 and also tried carb cleaner prior to the start but nothing.

-I Did check COMPRESSION and it checked out at exactly 120 PSI, even now it is 120.
- The carb has been rebuilt and checked over and over again for obstruction, assembly.
-brand new crank seals on both sides
-new base and top end gaskets- I did use copper sealant to for a top gasket for a tight seal/ torqued to spec. Base gasket had a light sealnt coat as well- can't remember what permatex I used rt off hand, but a nice job was done. I know it wasn't needed, but I wanted to assure myself a tight seal.
-carb, air mixture screw, I have played around with 1.5-2.5 turns out, usually leavin it 1.5 to 2. Throttle screw I have set 3.25 turns, didn't make any difference either way when i messed w it when it was running good.
- exhaust is good
-spark plug is wet getting fuel.

For some reason, I have a gut feeling that my problem is steming from the carb/intake area. ANY ADVICE WOULD BE GREAT!

 

Congratulations on getting it going. You sure have worked on this for awhile, I wish I had your patience. I think I would be talking to that first machinist about getting some money back.
Hard to say what your carb problems might be. Having sprayed fluid around the intake looking for leaks and finding non, I guess I'd be looking at the carb.

1 Float setting correct?
2 Float needle and seat leaking?
3 Throttle slide in backwards?
4 Needle in the slide not held in proper place with the clip?
5 The jets clean?

How is the fuel? Old / water in gas?
Good luck

 

Thanks Lovmudd

Yes, I have been working on this for a while and it has involved alot of patients, but I have been really busy with other things as well- so I havn't gone completely crazy yet working on it (learned alot though). Thanks for a list of some things to check.

1 Float setting correct? I did check it and it appeared correct
2 Float needle and seat leaking? Not sure, all is new so I would think not leaking but not sure. Not getting gas in crankcase.
3 Throttle slide in backwards? throttle slide only goes in one way
4 Needle in the slide not held in proper place with the clip? I set the needle in the same postion as the old one was. About rt in the middle I think it was. (If I remeber correct)
5 The jets clean? I have taken the new rebuild appart and recleaned it about 4 times. Looks super clean, but I guess I can't guarantee. When I first cleaned the carb when I purchased it, it was pretty clean to begin with. I guess I can't guarentee there is something partially blocked that I keep missing.


How is the fuel? Old / water in gas? Tank was pulled and cleaned and let dry for a week then new fuel was added. I have since put new fuel in it for a second time.


QUESTION- I did premix my fuel 50:1 w polaris oil for break in on the rebuild, but also was unsure if the oil pump worked. Is there anything I need to do If I assume oil pump is not working. I planned on premixing gas until I found out if the oil pump was working. But if it is not working, do I need to block off the valve on the carb that the oil tube connects to? THANK YOU