As some of you already are aware, I was having some issues with coolant blowing out my overflow, and eventually a total lock up where my clutch blew apart, and my rod siezed on my crank which was also siezed in one side case. I have since rebuilt it, everything is to spec and assembled correct, you name it it's good.

Upon riding it since, I have been pissed on again. It continues to blow coolant out, (even though my temp guage only says it's about 160-180 degrees F. And last night, I experienced something similar to the feeling I got from the machine when it locked up. It's kinda hard to describe, but I'll do my best.

When riding it hard at WOT in 5th, after a few minutes it feels like someone is pressing on the brakes. if I let off the gas, it coasts fine, but when I give it full throttle, it just bogs hard and really struggles. If I pull in the clutch, It revs fine and free, but once I let the clutch out it soon starts to bog again. It's not lack of fuel, it's not axle bearings, it seems like something after the clutch is heating up and getting tight. I noticed this same thing before it siezed up the first time.

If I just hold the clutch in and coast or even stop for a bit, when I start out again, it works fine but then shortly thereafter does it again. The time in which it works good is related to the time that it sits and cools or whatever.

I made the idiot mistake of checking my oil in the dark without a flashlight, thus resorting to using my lighter.......I am almost eyebrow and eyelash free today. I should have known better. I wanted to see how strong my return stream was, maybe there was some restriction, i don't know, but i do know there is alky in my oil.

So there is this situation, as well as my coolant boiling over, thus suggesting I'm running very hot. I'll post a pic of my plugs in my bio, they were new yesterday and pulled today. they are NGK DR7EA's.
My jetting is as follows:
95 needle in the richest position
Air screw 4.5 turns out
Uni filter on snorkle, no airbox
300 main
90 pilot

 

TheChosenOne here is my 2 cents.
What you are describing is a textbook lean condition. I mean you described it perfectly!!!!
I could be wrong but I think that is your problem.

I burn a blower engine down once. It felt exactly like you described. The problem was a 2 buck fuel fitting from the factory. It leaned up and the blower went bang and it melted 5 pistons in about 4 seconds.

Lets see the plugs. I bet they are tan.

 

Sparkplugs are too hot for one switch to a dr8ea or dr9ea some will even say a 10 I've run dr8ea's for 2 years on alky without a problem. My tm on alky stock bore with 14-1, 109 cams, ported head is as follows: 95 needle middle clip, 60 pilot 1.5 turns out, 4.5 needle and seat main 280, KN direct mount. I always use top end lube in my alky. hope this will help a little. Also check your cap, it might not be holding the pressure it should.

 

I as well feel that it's lean. Forgot to mention there is a deacceleration backfire as well. as for the cap, i have replaced it, and that wasn't the problem. I'm gonna try a richer main, around a 330.
The fuel fitting you mentioned, this caused the fuel supply to run dry and lean it out causing boom or what?
Cause I do have a slightly restrictive fuel line, but other than that, the petcock flows both res and on, and everything else should be fine, just never did change that hose. I'll check into that, and like I said richen it up and see if any problems are fixed..

 

If you had a restricted fuel line, you would drain your floatbowl when you are going flat out. I don't see how you could be running lean with those carb settings...........yet you do have lea symptoms. When i am running a bit lean, it shows up very quickly on my water temp guage. I find it difficult to believe you can pop the cap at only 160 degrees. Either the guage is inaccurate or you have compression leaking into the cooling system, IMHO.

Something else, when you replaced your crank bearings, did you carefully inspect the rod bushing at the crank pin? That will fail and start seizing the motor after you run for awhile allowing the friction and heat to put tremendous load on the motor. That will bring the temp up quickly and cause the motor to bog way down.

If you let it sit and cool for a short period of time, it will seem to go back to normal.

As that bushing deteriorates it won't take as long to seize up, you will get noticable slop to the point the piston starts ticking the valves at idle.

One easy way to rule this problem out is to check your drain plug for brass colored shavings.

By the way, the kind of load this problem puts on the motor will change the motor's jetting requirements as it seizes.

One more thing, seized carrier bearings will also have the same effect on the motor.

For whatever its worth I wouldn't run it now that you have rebuilt it until you find the underlying problem[img]i/expressions/face-icon-small-wink.gif[/img]

keep me posted.

Ron

 

One more thing, I would be willing to bet your alky that is washing into your oil took your crank bearings out. If it did that, it seems reasonable to me that your lower rod bushing might be compromised[img]i/expressions/face-icon-small-wink.gif[/img]

 

the pic of my plugs is on my pics page, I know it doesn't look good....Like you said Ron, it's hard to see how I'm running this lean with the jetting I have, but everything from the backfireing, the coolant, the plugs, and the heat on my leg points to a lean condition. I'm afraid as well of like you said....the alky in the oil washing down my bearings and such. I am running a redline top end lube, but that don't help bearings much.

I don't, nor have ever had any brass in my oil or on the plug/screen, which is a relief....And as for the cap blowing at 160 degrees, perhaps the sensor is a bit slow to recognize the temp change. Maybe this is because it heats up so quickly under extreme load and the position of the sensor itself limit it's responsiveness. By the time it reads 160, the coolant might already be at 200...who knows.

I think the answer must lie in the jetting. I'll run the DR8EA's with 335 main, 80 pilot, 95 needle in the richest clip and see what happens. I really want to stick with alky due top the fact I can obtain it for next to nothing, compared to 90 bucks for 5 gallons of race fuel. VP c-11 that is...

One more thing, I have the accel pump activated, and it seems to eliminate the bog as it does with gas. Does anyone else utilize the pump? or is that a nono? If anything, i'd say it would be benifiting me in this case...

Thanks guys...

 

The only thing I can think of is you are running way rich on the bottom (90 pilot and pumper) and that is washing down the cylinder walls, then you run lean on the 300 mainjet when WOT...........as unlikely as that sounds.

My buddy that runs alky closed off the pumper completely and eventually removed it.

What is your elevation up there?

 

2200 feet. Now you see why it confuses me this bad. I have tell tale signs of being lean, however I should be rich....it just doesn't add up.

 

i had the same problem after it sat for a couple months except it was popping and backfiring a lot under throttle. what mine ended up being was carb boot leak from the alky so went lean under any throttle.