Engine won't run right...

[Kachess]

I purchased a used bender rear mount RX-1,(with NOS, no head shim) a few years back and have never been able to get it run right. It blew oil out the exhaust, vibrated, and didn't develop power like it should. I finally stripped off the turbo/nos and realized the stock motor blew oil and ran weak.

I have just replaced the rings and have put 90 miles on it. I now have no oil consumption, have good compression on all cylinders, but the thing still runs exactly like it used to, like a dog. Sluggish, Slow to spool up and slow to come back to idle. Engine still only has maybe 80% power. Engine vibrates and has an odd exhaust tone. We have two other tons, and rode with 4 other tons yesterday and this feels like it has a totally different engine.

I've now checked and re-shimmed the head, leak tested the valves, replaced rings, gaged the cylinders. When I had the motor apart everything looked good and felt tight. I've swapped out coils, all elec boxes, and carburetors with a good running ton. All the plugs show good color and I know its running on all cylinders (pulled coil wires). I've had the sled overheat a few times since replacing the rings but am attributing that to the rings breaking in.

Since this thing was once turboed with nos I am now thinking it was damaged or they did something odd to retard timing. Is there any way to check or adjust timing? Could the flywheel be clocked? Could the crank be damaged and the engine still run?

I am at wits end!!

 

[Wildman]

How much leakdown did the motor have? Taper & Cylinder roundness? What A\F is the sled running under wot conditions?

 

[mbarryracing]

Good thought on the timing, common setup for NOS. Did you check that the stator wasn't rolled around to retard the timing?

 

[DV8]

If it was timing it could be down on power, But the vibration you speak of is what leads me to think its something else, crank bearing, rod, one of the two bent. It shouldnt have a vibration.

 

[kinger]

I'm with mbarry check your stator to see if the pick up is slotted. Still shouldn't be that much lower on power though.

carbs I assume are good? You have enough other tons around I'm sure you swapped everything by now. Who did the cam timing upon reassembly after the rings? That would surly cost you a ton of power if it was off a tooth.

 

[Youngton]

We have checked the stator and it has not been clocked. Can you check if rods are bent and if the crank is true with the motor still in the sled? If they are damaged, how do they effect power and throttle response?

 

[mbarryracing]

If a rod is bent, sometimes a tell tale sign is the compression in that cylinder is lower then the others depending on how much shorter the rod became...

 

[grassracer2001]

If a rod is bent, sometimes a tell tale sign is the compression in that cylinder is lower then the others depending on how much shorter the rod became...

hey apple barry..... want to ride i got the snowscoot all boosted up , sent it out in nov, and got it back at the end of nov......you know wat im talking about

 

[mbarryracing]

If a rod is bent, sometimes a tell tale sign is the compression in that cylinder is lower then the others depending on how much shorter the rod became...

hey apple barry..... want to ride i got the snowscoot all boosted up , sent it out in nov, and got it back at the end of nov......you know wat im talking about

grass smoker2001, yes, that is cause the short rod was on you, not in your turbo snowscoot... that, and your too nice...
How is that new dyno cell coming along?

 

[Rx1M5]

Did they slot the timing gear on the cam for the turbo install?
I did mine to the tune of about 2 degrees.

Rx1M5

 

[Kachess]

The gear on the timing chain was not slotted but the marks on the cams don't line up very well on their arrows while timing it. If the exhaust is on the intake is a little off. On my other sled they match right up, but on this sled if one cam lines up the other is off a little. I also noticed the chain did not nest down in the cam sprockets very well. I wonder if the cam chain has stretched. Could that affect running enough to my symptoms? What would cause a chain to stretch? My other sled with 10k miles the chain nested fine and marks line right up.

If the timing chain is it, how much engine disassembly will be required?

 

[Sled Dog]

The gear on the timing chain was not slotted but the marks on the cams don't line up very well on their arrows while timing it. If the exhaust is on the intake is a little off. On my other sled they match right up, but on this sled if one cam lines up the other is off a little. I also noticed the chain did not nest down in the cam sprockets very well. I wonder if the cam chain has stretched. Could that affect running enough to my symptoms? What would cause a chain to stretch? My other sled with 10k miles the chain nested fine and marks line right up.

If the timing chain is it, how much engine disassembly will be required?

I would say that could very well be the problem valve timing is very important to making power. The sprockets are probably C cut a bit and yes chains do stretch especially if it was turboed.

 

[jd0270]

Have you checked the condition of the tensioner?, there is a wear limit spec on the chain that you could measure. I doubt the chain has stretched though. Your timing needs to be corrected though, one tooth out makes a world of difference.

 

[Kachess]

I replaced the timing chain and timing is now dead on. Engine runs slightly better, but still off on power, does not wind up fast, and has the strange growl for an exhaust note. I rechecked compression, and all plugs look equal and are a nice tan.

Running out of ideas I decided to check the pick-up coil resistance and it shows 188 ohms (at 25F) for a split second and then reads open. I tried my other two tons and they read in the range and and stay. I figured maybe it was the connector and stripped the wires and still get either an open reading, or just a instant flash of 180ohms. I tried another multimeter and still cannot get a constant resistance reading. I can't imagine what failure would allow it to only read a resistance for a split second.

I'm going to try a new coil but was wondering if anyone else has had this experience, and could a bad coil create my motor's symptoms?

 

[mbarryracing]

Electrical gremlins can do weird things... I wouldn't rule anything out.