Engine problem

mvmccreary · Jun 30, 2015

On my way home from thunder my bike shut down about 40 miles from home. I stopped for gas and it was running fine, when I started it up ten minutes later and went to take off, there was no power at all. I felt like I was riding a scooter. I couldn't figure it out, it wasn't making a bunch of noise I thought maybe I was just really really low on gas when I stopped and it needed a minute to catch up? I don't know, but two miles down the road I thought I heard a light "clunk" and the engine died. I was rolling about 10 or so miles an hour so I let the clutch out to get it going again, and the bike jerked and stopped.

So I'm home now, and I was trying to spin the crank shaft (while the plugs were out) and there is a point when I can't spin it any further. I took the oil pan off and there was nothing obvious in there, I haven't pulled the screen off the pump yet but from what I hear it should be extremely obvious if a bearing spun. So what's my next move. Where should I look next to try and see what the hell is going on with this motor?

Note the two rear spark plugs were quite fouled and wet, where the front plugs looked normal.

one2dmax · Jun 30, 2015

Usually there will be debris in the pan if it spun a bearing. I have seen a few rare instances were a valve failed and started to drop into the cylinder. This gets really bad if it manages to pull it all the way in which then destroys everything.

I have broken a rear intake cam as well which sucked and killed power but it didn't seize things up.

You can look up into the cap area and see if you can see bearing material squirting out of the sides of the cap. You can even rotate the engine and pull each cap one at a time and check/reinstall it. Use caution as there is an orientation to the cap as well.

Fire-medic · Jun 30, 2015

I have had both of the issues Sean has described, a broken rear intake camshaft and a spun big end rod bearing. The rod bearing sounds like what you described though I was close enough to home I got there w/my junk engine.

Your best bet $-wise is probably going to be another engine to replace yours. Rebuilding yours if it's capable of being rebuilt: crankshaft is toast, 1 or more rods, same, and possibly the case thrust surface. Plus whatever damage the pieces did in the oil film of reciprocating parts w/tight clearances. A teardown is obviously the way to find out.:confused2:

mvmccreary · Jul 1, 2015

So what's next?

Dragmaxster · Jul 1, 2015

mvmccreary said:
So what's next?

Is that the cam chain lying at the bottom of the blurry photo?

mvmccreary · Jul 1, 2015

Dragmaxster said:
Is that the cam chain lying at the bottom of the blurry photo?

Thats correct :bang head:

Dragmaxster · Jul 1, 2015

Looks like the camshafts are coming out- you can get a new one on Ebay.
Look carefully down below.

one2dmax · Jul 1, 2015

That bites! You could try installing a new chain (which can be done without removing the heads or splitting the cases) but there may be some valve damage. If you get a used cam chain (which I see no problem with) then you have to split the cases, pull the heads, remove and mark the piston caps, and then you can lift out the crank to slip the chain over.

mvmccreary · Jul 10, 2015

Found this in the oil pan after further, much closer inspection.

sdt354 · Jul 10, 2015

At this point I'd want to know if valves are bent and or piston wrecked. A cheap bore scope for piston inspection will save dissembling time. You shouldn't have to remove the head or split cases. Let me know, I've got what you need including a chain. But I'd go with a split chain for sure. I believe they are available new. Or maybe take a rivet out. I think Sharky split a chain recently. Check and see if the valves closed. You can rotate the cams now and see if valves move freely & close. There may be salvation for this engine, I hope. Sorry this happened, you worked hard on this bike Matt. And it's got sentimental value, being you Grandfather's ride. Call PM or e-mail me if you need a bore scope or parts. I might have everything. On further review I see it's a piece of the cam that supports the gear.

maxcruiser · Jul 10, 2015

After seeing that it's a broken cam chain and the fact that you mentioned that you tried to bump start it and the bike stopped dead, I would think that some of the valves are bent.

It doesn't take much force to mess them up.

Mike

mvmccreary · Jul 10, 2015

sdt354 said:
On further review I see it's a piece of the cam that supports the gear.

Steve, I was going to email you with this picture and I thought the same exact thing, since the bolt was the same size and everything. I am pretty bummed but I still have my original engine I can mess with.

Dorney · Jul 10, 2015

The 1 pic he showed looks like the chain blew a chunk out of the head. Is it possible that the cam chain tensioner went bad & the chain wadded up?

one2dmax · Jul 11, 2015

The chain will indeed wad up and lock up the engine. You'd have to examine it to see if and what damage happened. Odds are the valves closed unless they stopped at the very top most position and not likely damaged.

dingy · Jul 11, 2015

There could be some broken teeth on the crankshaft cam drive gears. This can happen when cam chain bunches up under crank.

Picture shows (poorly) 2 teeth missing on crank that I did when tightening rotor bolt and tool holding clutch basket slipped allowing crank to rotate. Heads were not on at time so chain was slack.

Gary

sdt354 · Jul 11, 2015

dingy said:
There could be some broken teeth on the crankshaft cam drive gears. This can happen when cam chain bunches up under crank.

Picture shows (poorly) 2 teeth missing on crank that I did when tightening rotor bolt and tool holding clutch basket slipped allowing crank to rotate. Heads were not on at time so chain was slack.

Gary

Good post for you Matt from Gary. This must be checked. This engine might be salvageable. Like Sean said, valve may be ok. But I am an optimist.

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