OPT, I have checked the rod and crank assembly and there is NO play that i can feel and smooth rotation. Looks clean in the bottom as well. When I pulled the jug off today and looked into the bore I can still see the cross hatches in areas that are not even touched. Like the rings never made contact with them (is this normal - aprox. 20 hours run time).
Also with my checking i still have a full oil resivoir, i would think that in two years of off and on riding that i would have to fill that thing up. going by the 40:1 ratio i should go through 1 gallon of oil to 40 gallons of gas, correct? I am leaning now that the injection part is not working? Is that operated by vacuum or pump? Also should I replace the reed valve? and what would be the best piston (cheap) to get (brand)? Thanks again for all the input, got to keep the old machines alive!!!

thanks,

Fire3096

 

If you have been running for TWO years you are getting oil!! You can check the pump out for operation and see if its spring isn't broken or pump frozen up. Lot of people block off because of fear or some do if pumps are frozen. You can take the 10 mm bolt out from the injector line at the cylinder and should be able to feel a little oil! Perhaps the person who did the cylinder just stuck a std piston and rings in??? That's why I said to have the cylinder properly measured!!! Could have worn the rings out because of too much play to begin with! Have the cylinder measured against the existing piston to know where you stand!
Optimum piston to cylinder clearance is NO more than .002 clearance! I always tried to get .0015-.002 when I bored cylinders. At .005 clearance for all purposes the piston is worn out! I've had em come in clattering,still trying to run with clearances past that! Another thing is you will not use a lot of oil in the injection system,one of the first things people have asked in the past. Rule of thumb is 5-6 tanks of fuel to 2 quarts oil! Some more some less! I think the top end was not done Properly!(HALF AZZ JOB) I've seen plenty of them come in the shop over the years! As far as reeds,just check for any fraying,split ends,broken petals,warped ends to where a lot of light is visible through them,if they look ok you can reuse. Let someone reputable check this engine out and if you have to rebore use a WISECO piston only! OPT

 

OK everyone here is the update. Rebuild on the top end and have good compression, not great but near 100 to 110. I put it back together, Mixed my gas and placed that directly into my tank. Tried starting - - - would not fire. Pulled plug grounded it to the frame, orange spark. _ changed CDI box, rectifier and limiter. Plug same orange spark...I have new coil going to put that on next. But after trying above - - - Tried starting and BOOM backfire, blowed pipe off jug. Tried again - - - BOOM backfire, same effect! will not start then backfire ( turns over and over and over and BOOM !) where should i look next?
New bore.
new piston, rings and gaskets.

Could the case be cracked?
Bad reeds?
timing? how?

Please point me in the right direction, I am starting for the gas can and a match.........or a DEEP hole!

 

First off compression is still low for a new top end!! Should be around 130-140 psi or more if done right
Plus have you checked the slack on throttle cable so that limiter switch is not causing the backfire problem? OPT

 

OPT, when you say slack on the throttle you are talking about the ETC in the throttle control. and if so when at idle the switch should be open, throttle operating should close it correct....? And is there a way to test that curcuit to eliminate that?

Thanks,

Fire3096

 

On the older etc systems the thumb throttle just has to be fairly snug with out any play,but make sure idle doesn't change when you turn the bars. If idle increases,just loosen cable adjuster and turn in a little. The newer style had about 1/8' play at the thumb lever. OPT

 

Another update, Kinda feel stupid...I was going to check the wiring from the stator and pick up today, Pulled the flywheel and found that the woodruff key was sheared completly in too and the flywheel had rotated an unknown amount. Fly wheel key way is now fouled up - "wallared out"....crank keyway still good as new. Placed a new key to check it, replaced everthing - Started right up......kinda missed a little. Pulled flywheel again to check and halfway sheared another key. Guess i need a new flywheel for a '96 400! Unless anyone has one for FREE? (wink). I failed to K.I.S.S. - Live and learn!

Thanks for all the input, and serious - If anyone has one for free let me know!
LOL.

Fire3096

 

Could try Rick Ritter. (618)644-3211 He has lots of parts around. I am actually heading down there Friday to drop my 1996 Scrambler 400 motor to have the lower end rebuilt. This guy checked out my cylinder and piston and told me the piston was worn and not the cylinder( like my local polaris dealer) Saved me alot of money. Real stand up guy. Id call him though it wont be free , hes very reasonable.

 

Here is the update, I have my machine back up and running! I have removed the oil injection and blocked it off. New top end! I found the problem of the keyway or woodruff key sheared and the flywheel (and timing) spun on the crank. I put the flywheel back on and sheared another one. I had to resort to the universal key (lincoln). still would not rev up. pulled flywheel again, adjusted the timing and had it to the mark again still would not go full throttle. pulled flywheel the last time and adjusted the timing to the max. reinstalled the flywheel again. runs like a a champ. full rpm and awsome power. i would like to say thank you for everyone's input cause it helped out alot. all i need now is put a new hub coil on the right side to fix my 4wheel drive and my machine will be back to 100%. again thanks to everyone!

and also please dont give me too much grief about the lincoln key!!! LOL!

Fire3096