Following a motor change I apparently have a new issue.

After putting together a crank trigger system on the newer 12a I run in my sand rail, the car started and idled better than it ever had and had great throttle response. This newer motor is a stock 1983 12a that had sat in someones garage for a number of years. I run a ported racing beat intake, 650 Holley, 2" ID dual straight pipes and a 150 hp shot of nitrous (and a snowmobile clutch drive, no tranny). I took it to the races a couple of weeks ago and on my first pass I had, what I thought was a nitrous solenoid stick open and flooded the motor. I pulled the plugs cranked it until it stopped blowing fuel out the plug holes, put new plugs in and it started up only to bog down and stall then apparently going into carbon lock. It took 4 days of WD-40 and hand cranking to free it up, another two days to get the oil out and get it to stop soaking the plugs.

Now the bigger issue. Some times it will start, rarely though. When it does, it runs good for about 20-30 seconds and then bogs down and stalls. When I go to restart it the motor turns over like it's really tight, almost seizing up. I changed battery cables, the battery is a fully charged deep cycle, put in new starter, no difference. I have a good strong spark. With the plugs are out and I'm cranking it, I get alot of black fuel spray out of the front hole and little out of the rear. When cranking it over I get what looks like black smoke out of both pipes. (carboned up fuel?) I tried the back up carburetor and no better. I have not done a compression test but both holes have alot better push back on a finger test than the old motor had, and when it was running before the race, I had equal strong exhaust pressure and both plugs burned very clean.
Do I need to do some kind of wash out to get the crap out of the motor or have I lost a side seal or what?

This clip was shot before the race.

 

Are you sure its fuel and not water?

 

No I'm not. I have a closed cooling system (remote water pump and motorcycle radiator) and really don't have any way to check for coolant loss. When it was running I didn't smell burning antifreeze and I didn't think the coolant had any direct access to the combustion chamber.... and the oil is still clean! I guess I could drain the system and see if that stops the problem.

 

Hi Darryl . You have probably checked all this but here goes , I have had huge flooding issues with the dragon . When deflooding the engine I found that I had to turn it over for a few seconds many times to deflood it and then would do exactly as you describe , Immediate start up and just bog down ,fire out the headers sometimes ,and DIE with out a puff. One time it took me a week of turning every few hours and let sit with plugs out and throttle plates propped open . starting fluid seems to help dry them out without ignition just turn over give it a shot and turn a bit more and let sit again .

I know you are not new at the holley carb but I guessing maybe you had it apart for what ever reason and possibly have the gaskets mixed if they are wrong the carb will pour huge amounts of fuel into the little engine when attempting to start . why do I say this ?? because I have done it , It's becomes so simple to dismantle and reassemble that I just didn't pay attention . I tore it down twice before I caught it and after fixing the problem . I even took the air hose many times and blew air in the plug holes = turn 1/3 turn blow again turn 1/3 again blow ,, Both rotors a few times .. It seems to be the nature of the beast instead of blowing ALL the fuel out the plug holes it just rolls it around and around blowing out some . I would also suggest that you loosen the float bowl screws and drain all fuel from the carb and not refill untill after you have started it and maybe primed it a couple times .

If you have your headers off check the apex seals and make sure they are not stuck up with carbon .

 

could be an oil starvation issue or a bur on a bearing surface.

 

I am going to try draining the coolant out of it for starters, then flush out the chambers and see if it clears up with that. It started and ran really good until I topped off the coolant the night before that last race. I already tried swapping the carb out to see if that was somehow contributing and it made no difference. I have the 650 Holley and a 600 Edelbrock that are both set up to run on this motor.
We have another race in two weeks but I'm probably going to focus on finishing up my sons toy to play on for that one. It is may more radical than my little buggy.... It's a 300# quad with a 700 Yamaha SRX triple something like 182 hp.

 

sorry to say but it sounds like a spun bearing issue.