I am in the Air Force forward deployed atm, and I have been racking my brain trying to figure out this machine.. First off, it has been sitting outside in the driving sand for who knows how long along with another 6x6 thats had a lot of parts picked from it. I was told by my supervisor to try to take the 2 machines and make 1 functioning one.. Ok, first things first.. I have changed the oil and all filters, removed the carb (had filter elbow disconnected), and carefully took it apart taking note on where everything went, cleaned it out, re assembled, reinstalled, but didnt connect the fuel pump or fuel line. I took out the plug, cleaned it, put it in the wire boot, leaned it against the head, and cranked it over and it had a powerful spark. I took out the tank, put about 1 gallon of fresh gas in it and shook it till all of the particles were loose then flushed it repeatedly with more fresh gas till all of the gunk was out, re installed tank, and replaced fuel filter and all lines, hooked everything all up and gave her a crank, no go.. I get SOME backfiring through the exhaust, but it wont run.. I googled my problem and found that the CDI regularly goes bad, so I switched it with a known good one, and still no running.. I even took a carb off of a good 6x6 (running) along with its CDI, nothing.. I put the rebuilt carb and good CDI on the good machine and it would only run at 1/2 to full throttle, and really badly at that, backfiring through the exhaust.. Next I pulled the stator/flywheel cover off and did a visual under there, removed the crank position sensor and inspected the face of it and it looks cracked in the middle, could this be my problem? How often do these things jump time or stretch the timing chains? Oh yeah, I checked compression (dry then wet) both times net approximately 115psi with VERY slow leakdown. Unfortunately for me, we dont have a service manual yet, but it has supposedly been ordered.. Thanks for any help!!

SSgt Natehan Sanders


Almost forgot, I disconnected every electrical connection 1 at a time and cleaned them thoroughly with aerosol electrical parts cleaner, then blew dry with compressed air, well, almost everything...  

what size engine??

a 250cc polaris engine should have approximately 130 psi. and larger engines more.
so 115 psi is enough to make it not want to start.

if the carb is causing issues on the good machine, then you'll most likely need to adjust the fuel/air mixture.
cutting out is a sign that it is not getting enugh fuel, while bogging down is a sign that it is getting too much fuel in the mix.
turning the fuel/air mixture screw to the the left will add more fuel into the mix, and turning it to the right will decrease the amount of fuel in the mix.

mark where the fuel/air mixture screw is when you start, and keep up with the number of turns you make.

normally 1/4 turn increments work best to tune the mixture.

Oh and thank you very much for your service in the military.
without you guys we'd be another Iraq or korea with no rights at all  

Hrmm, what size engine I dont know, it has a mikuni slide venturi carb.. Is the mixture screw the one that the choke cable runs through? if thats not it, theres not one, the only other adjustment is the idle speed... Oh well, I will do a compression test on the other engine and see where it leaves me. I have been told that our service manuals will be here in less than 1 week, but I will continue on testing what I can and see if I hit pay dirt. Do you know if there are any obvious timing marks that I can find on the chain and sprockets? I think my next dig will be pulling the crank angle sensor off of the good machine and swapping it onto my little frankensteinranger, I can also turn the engine to TDC and see if the intake or exhaust valves are open as well to see if the chain is stretched or skipped a tooth. One more question: of the 6 wires running into the stator cover, 2 are the crank angle sensor, what are the other 4?? are they for the stator? Thanks for your help and kind words! Remember, when you see those bombs going off, they were " brought to you courtesy of the RED, WHITE, and BLUE"!!

SSgt Nathan Sanders  

look on the cylinder, the engine size will be stamped on it  230ccm or larger or smaller.

on the timing chain and crank there should be some type of timing mark.

til your manuals get there try looking on this site for a service manual for free online copy

http://manuals.dqt.be/index.php?option=com_remository&Itemid=36  

Thanks for your help Wolf, I will check into things and get back to you!!

SSgt Nathan Sanders  

Well, I am back and found out really quick that our compression gauge was bad.. I borrowed another one and re-tested and found that my machine has about 35 PSI dry, and with about a teaspoon of oil in the cylinder only yielded 50psi. I removed the head and cylinder yester day and found my problem... The top of the piston and cylinder is BADLY scored, oil on the back side of the piston is coked up (only on the burnt side). I also found out that the exhaust rocker has a deep groove through the cam contact pad where it rides on the cam lobe (on top of the decompression valve). If I can find a digital camera here, I will post up pics of all of the carnage, its pretty gruesome!! I am about to order a slew of new parts for her (including carb parts) to get her running like new again. What do you think caused the scoring on the top of the piston and cylinder? I mean its so bad that the aluminum from the piston is fused over the rings!!!

Thanks, SSgt Sanders  

you nev er can tell, i have seen a large amount of water in the cylinder score the piston up pretty badly during combustion.
but with the other wear it sounds more like it wasn't oiling well.

if you need to send the cylinder to me and i get it bored out fairly cheap for ya.

check out www.rjatv.com for a good piston and top end kit.  

Thanks for the reply, I was told to order a new cylinder after our machinist looked it over and said theres more than .050 deep grooves in it, so its getting a new piston, wrist pin, cylinder, cam, exhaust rocker, oil pump, water pump, and all associated seals.. I'm guessing the piston is splash lubricated, and the idiots that operated it never checked the oil level and thats what caused the damage.. Or it had a hard time starting and it got ethered.. Either way, it is getting a top end rebuild, and the head will be getting a mild port job by me along with a combustion chamber smoothing, as well as unshrouding the valves as much as possible. I want to sincerely thank you for your help and replies, you have been a big help!

SSgt Sanders