Installed Hot Cams Now Backfiring

[coolhuh]

I installed the Hot Cams in my YFZ, when I tried to start it, it backfired real loud out the exhaust. It did not even try to fire up. I have the motor at TDC and the little dots on the cams are straight up and to the outside of the case, the lobes are pointing away from each other and the "I" mark is lined up with the stationary mark. It sound like the timing is off, so how do I make sure it is correct?
Thanks

[yfz450les]

Originally posted by coolhuh
I installed the Hot Cams in my YFZ, when I tried to start it, it backfired real loud out the exhaust. It did not even try to fire up. I have the motor at TDC and the little dots on the cams are straight up and to the outside of the case, the lobes are pointing away from each other and the "I" mark is lined up with the stationary mark. It sound like the timing is off, so how do I make sure it is correct?
Thanks



line ur flywheel then when its lined up make sure that the dots on the cams one is lined up with the case and one shuld be almost be straight up and make sure your chain tensioner is tight.hope this helps

[Trx4Life]

I know since I did my old ladys it pops a lot, Espicelly when you run it hard and let off it starts poping bad. I was told it was way to rich????

[bnbracin12]

I build and maintain 15 YFZ450's from 04-06, as well as TRX450R's. From my experience, lining the marks up at the flywheel doesnt always give you an acurate TDC. what seems to be the best way to get TRUE TDC, is to remove the spark plug, and insert a long philips screw driver into the cylinder, remove the plug on the IGNITON side, (same side as timing marks) and turn the motor over with the 17mm nut very slowly. until your screw driver gets to its highest point. As long as the cams are facing opposite of each other, and the screw driver is at its highest point, that is your true TDC. line the mark up with the dot at the outside of the head, I.E.-exhaust side, dot outside toward the exhaust pipe, and the other dot at a 90 degree agnle, at the top of the head. Intake is the exact same, except dot is facing carb, and 2nd dot is perpendicular. Some things to look out for:
once your on TDC and marks are lined up, make sure your tensioner is tight and then move the motor back and forth slightly to make sure your on TDC. then put it all back together and it will be in time and will start right up.

[coolhuh]

Thanks for the information, I am going to the garage right now to get it running.

[daddio]

Did you check your valve clearance? Hot camms are a little tighter than stock. I had to re-shim mine. But I don't have the backfire problem and it runs great.

[coolhuh]

I got it running but it does not seem to run real smooth. It idles smooth but when I ran it at around 3000rpm for break in, it runs a little rough, but no backfires. If I hit full throttle real quick it sounds great. It also will not start unless I give it a little gas. Could this be timing or jetting. I have a HMF pipe, airbox eliminator w/K&N, now hot cams and 170 main 45 pilot NCVQ needle clip in middle.

[daddio]

With the hot camms, it is very important that you get the valve lash as close as possible. It should be .15mm intake and .20 exhaust. I set mine to the stock specs and it ran like crap. I changed it to the hot camm specs (after calling hot camms and complaining) and it rips, now.

[bnbracin12]

the roughness at 3000 is a combination of the new hotcam and the jetting. the jetting with that pipe sounds pretty close. What other mods do you have.? Ported? Valves?
The best way to check to see if your jetting is close is to look at your exhaust tip, it should be a chalky whitish grey color, if its simply black, then its a little fat, but that ok as long as it doesnt cut out on the top end. If you have any other questions just ask and ill be more than happy to help. I ride and race a YFZ450 and it produces 71 hp to the rear wheels. its an amazing bike that produces excellent power, and the mods i have are a combination of my own tricks as well as other add on's available to the general public. its ported for my riding style, stock size valves, 439cc, 14.5:1 compression wiseco piston, stock intake cam with alternate timing, hotcam exhaust cam, trailtech heavier flywheel, curtis sparks custom exhaust/big bore with shorty megapohone, stock carb with 205 main, 60 pilot, curtis air intake kit, curtis sparks dyna ignition box, and as well as a few other little tricks here and there to make it faster.



B & B Racing

[coolhuh]

I am headed to the dunes today and I will see how it performs. When I get back I plan on having it ported and polished.
I took the hot cams out and put it back to stock w/cam mod.