r2nailer Posted January 23, 2012 Report Share Posted January 23, 2012 I have a 99 shee that was a recovered theft.That sat around for a few years. It was run without premix. I honed the cylinders and replaced pistons and rings. The rings have an end gap of about .014" Compression is only at 70 lbs, but the rings havent seated yet either. If I prime the cylinders it does fire but won't run. I found vacuum leaks at both reed valve blocks and added gaskets. But It still won't start. It doesn't draw in any fuel. I thought the 2 crank seals must have been beat up so I replaced them also. No joy. I injected low pressure air into one cylinder, and could see evidence of it in the second cylinder. So at this point I must ask are the two cylinders isolated from one another like all the sleds I've worked on? There no indication of a center seal or bearing in any of the part diagrams I'v looked at? Opinions welcome...... Quote Link to comment Share on other sites More sharing options...
raptoreater Posted January 23, 2012 Report Share Posted January 23, 2012 I have a 99 shee that was a recovered theft.That sat around for a few years. It was run without premix. I honed the cylinders and replaced pistons and rings. The rings have an end gap of about .014" Compression is only at 70 lbs, but the rings havent seated yet either. If I prime the cylinders it does fire but won't run. I found vacuum leaks at both reed valve blocks and added gaskets. But It still won't start. It doesn't draw in any fuel. I thought the 2 crank seals must have been beat up so I replaced them also. No joy. I injected low pressure air into one cylinder, and could see evidence of it in the second cylinder. So at this point I must ask are the two cylinders isolated from one another like all the sleds I've worked on? There no indication of a center seal or bearing in any of the part diagrams I'v looked at? Opinions welcome...... i would throw a new crank in. get one cheap off ebay. Quote Link to comment Share on other sites More sharing options...
sprinklerman Posted January 23, 2012 Report Share Posted January 23, 2012 they aren't isolated from each other, so the air passing to the other cyl is normal. If it was ran too long w/o premix ,then the crank is prolly in a bad way. (not that that is why it wont start) You should have more than 70 PSI on a fresh rebuild even if the rings aren't seated as well. Quote Link to comment Share on other sites More sharing options...
ticktock Posted January 23, 2012 Report Share Posted January 23, 2012 The cylinders, we're they grooved bad from the no oil damage? What do the cylinders mic out at? Are you testing compression WOT? Are the carbs cleaned? Even before the rings seat you should have more compression than that. Adam Quote Link to comment Share on other sites More sharing options...
Jereme6655 Posted January 23, 2012 Report Share Posted January 23, 2012 You say that you honed and replaced the pistons and rings......but did you bore the cylinders? It could be that the jugs were already starting to be out of spec when the thieves burned the motor up.....chances are it isn't starting because you need it bored. They really need more than 100 psi to start.....and even if the rings AREN'T seated yet..l.l.30psi is a lot to make up Quote Link to comment Share on other sites More sharing options...
RadarRacing Posted January 23, 2012 Report Share Posted January 23, 2012 Did you install the pistons with the windows facing the wrong way? They are supposed to face the reeds NOT the exhaust side. 100 psi is about the minimun to get any motor to start. .014 doesnt seem excessive for ring end gap. If it is set up for a different piston like if it has a different crank, stroke, rod combonation you can have probs. There are different dome angles and, pin to crown heights. Quote Link to comment Share on other sites More sharing options...
r2nailer Posted January 23, 2012 Author Report Share Posted January 23, 2012 The bores were mic'd about 42.25 The windows were facing the reeds. I reran the compression test and the carbs were off as well as the pipes from previous testing and they were just over 100 lbs. There just seems to be little or no vacuum to draw the fuel in. But I may be wrong, 95% of my experience is with 4 strokes. Quote Link to comment Share on other sites More sharing options...
themechanic Posted January 23, 2012 Report Share Posted January 23, 2012 how can the bore size be smaller than stock, 64mm is the stock bore size. piston side wall clearance issue. what was the clearance?? Quote Link to comment Share on other sites More sharing options...
blowit Posted January 23, 2012 Report Share Posted January 23, 2012 Your compression (or relative reading from the gauge used) seems low if cylinders are not ported. However, the primary mode of intake function is crankcase vacuum when the piston is going up. In short, the compression does not largely affect fuel draw as much as ring seal and piston clearance. The very first thing I would do is verify you have a schrader valve in the tip of the test gauge insert used. I would also recommend you clean the carbs and/or add some raw fuel to the intake to confirm it wants to run. If it fires up with fuel added, get the carb apart and start there. Inspect the pilots first. Quote Link to comment Share on other sites More sharing options...
r2nailer Posted January 23, 2012 Author Report Share Posted January 23, 2012 well I lost my reply so here goes again. My snapon compression tester was in need of service and the compression reading is now 115 and 120. With no pipes or carbs and only 1 reed block. I had checked the jets previously when I replaced the needle and seat. But I pulled them apart anyway. I did find some restriction in the orifice of one of the jets, so the carbs are soaking in the cleaner. Tomorrow is another day.... Steve Quote Link to comment Share on other sites More sharing options...
blowit Posted January 23, 2012 Report Share Posted January 23, 2012 Soaking will probably not do much good. If you found restriction in the jets, clean them out and run it. Should take 30min to fix this. Also verify the choke plungers are working correctly. One pulls the other via vacuum Quote Link to comment Share on other sites More sharing options...
r2nailer Posted January 23, 2012 Author Report Share Posted January 23, 2012 (edited) no the restriction was in the hole the jet came out of. I cleaned the jets when I replaced the needle and seat. How is the float height measured? How do I verify the choke? Edited January 23, 2012 by r2nailer Quote Link to comment Share on other sites More sharing options...
blowit Posted January 23, 2012 Report Share Posted January 23, 2012 the emulsion tube is an easy remove/clean/install. Since you messed with the needle/seat, you now have me wondering if the bowls are filling up at all. better check into that. The screw on the bottom of carb is a drain. Float level is likely a non-issue here. Choke are plungers. Need to move freely, and no damage to cross tube that connects them. Quote Link to comment Share on other sites More sharing options...
r2nailer Posted January 23, 2012 Author Report Share Posted January 23, 2012 yyup checked the tubes, there good. Bowls had fuel in them when I pulled them apart, enough? I would think so. The left cylinder bowl has the extra brass tube right? Quote Link to comment Share on other sites More sharing options...
blowit Posted January 23, 2012 Report Share Posted January 23, 2012 yyup checked the tubes, there good. Bowls had fuel in them when I pulled them apart, enough? I would think so. The left cylinder bowl has the extra brass tube right? Yep. Do you have the slides in right? They can be reversed right to left which makes the chamfer on the bottom point towards engine. You want them towards the filters. Also TRIPLE check the pilots. I lost count of how many we have fixed. They are tiny and plug easily and they pretty much will not run without. Quote Link to comment Share on other sites More sharing options...
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