Originally Posted by boogaloodude

Check for exhaust leaks, they're frequently the source of backfiring. Even a little leak at the muffler to header joint can cause some loud backfires. Make sure everything is buttoned down good.

If your compression is fairly equal on both cylinders, your cam timing is almost certainly correct. If your cam timing was incorrect, you'd have a big variance between the two cylinders. Make a couple of vtune runs and see if it starts to work itself out.

I did a 107 build with tw8 cams this winter, when I first fired up the bike on a map for se257 cams, I was getting all kinds of snorting and bucking, but vtuning worked it out pretty quickly.

These things can be very sensitive to exhaust changes or problems. I got my bike half-tuned with one set of baffles, decided I didn't like the way they sounded, so I switched them out, and it felt like I was starting from scratch on my fuel map.

Originally Posted by Crazy

I agree about the cam timing. The good compression test leads me to believe that the cam timing is OK.

The thing is, it won't start at all, so no vtuning. The starter motor spins the engine, which does nothing except give a loud backfire every 5 to 10 seconds. (and I mean gunshot loud)

I've got some things to do this morning, but later I'm going to try to start it with 1 sparkplug removed at a time. I'd like to see if both cylinders are acting the same, or if one is different than the other.

Thanks.

Originally Posted by Crazy

The thing is, it won't start at all, so no vtuning. The starter motor spins the engine, which does nothing except give a loud backfire every 5 to 10 seconds. (and I mean gunshot loud)

Originally Posted by djl

Check the plug wiring, sounds like you have them crossed.

Originally Posted by Crazy

Yes, YES, YOU are CORRECT, sir!!!

As soon as I read your reply, I knew that was it.

As far as all the other possibilities went, I figured that they were unlikely. This job took me a long time, because every time I did something, I'd make sure of it. Then, the next time I came back to the bike, I'd double check my previous work before doing something new. The next time, I'd triple check the first thing, and then double check the next thing that I had done after that first thing, and so on.

The spark plug wires were the last thing I did before trying to fire it up, and I just plugged them in without a second thought.

Not the first time I've been a dumbass.

Thanks again.

Crazy

Originally Posted by boogaloodude

sorry, I misunderstood your last post, when you said you'd loaded the 255 map, I jumped to the (wrong) conclusion that you were running at that point.

I think dj's right, check your plug and coil wires, it's bound to be something fairly simple. Your cylinder pressure is right where it should be for your altitude, your cam timing and pushrod lengths are likely all good.

Did you go through the rockers, or are you using quickee pushrods?

Originally Posted by 07 dyna man

well how does she run now with the cams and the bump in compreesion