1970 Ambassador timing troubles

[Billiam]

Hi,

I built my bike out of a garage full of parts belonging to a Friend. The pieces have come together pretty well, it's almost done. I timed the engine before it went into the frame, but when it came time to fire it up, no joy. Now I'm going through the timing process as described on This Old Tractor, with the engine installed in the frame. I've been through the process five times, slowly and carefully, but always when I install the #2 exhaust valve rocker and turn the crankshaft, the exhaust valve hits the piston. The numbers on the degree wheel aren't lying, so I'm wondering if I've somehow got the wrong cam or pushrods installed in my engine. My feeling at this point is that the next step is to pull the cam and check it out with a caliper. Anyone out there ever encounter a problem like this?

 

[john zibell]

To begin, there are timing marks on the cam and crank gear. Did you align them on assembly? The mark on the cam gear will be a 6 o'clock and the mark on the crank gear at 12 o'clock. The oil pump gear has no marks so don't worry about that one. Let us know if the marks line up. The crank gear turns twice for each revolution of the cam gear.

 

[Amboman]

From the factory there is also a paint mark indicating which hole of the cam gear the dowel for the camshaft should fit into.

 

[Billiam]

Hi,

The crank and cam gears on my bike are unmarked, except for the paint mark indicating which hole the cam gear dowel pin should go in. I assume that the gears were originally marked with paint which wore off over time. I used the flywheel timing mark when I first timed the engine. The cam had been removed, I reinstalled it. Though it seems unlikely, I wonder if I have the wrong cam installed. I've established TDC with a piston stop and a degree wheel, turned the crank 122 degrees clockwise from the front, turned the cam counterclockwise til the .50mm clearance is taken up on the #2 exhaust valve, installed the cam gear, and then when I install the #2 intake rocker and turn the crank the valve goes bang into the piston. Strange stuff. I'm going to pull the cam and mic it on Monday, I'll let you know how it goes. Thanks for your responses, much appreciated.

 

[john zibell]

Look closer at the gears. I've never seen gears that weren't marked. May just be a dot, or a short straight line into the metal. If all else fails, these gears are still available. These are the same gears used on the 1972 Eldorado.

 

[fireflyr]

This is an Eldorado 850, but similar.

 

[fireflyr]

Oops. Forgot my 750 was all gear driven. I have it somewhat pulled apart and am not going to use it if you run into a problem with a lifter or cam.

 

[Billiam]

No punched, cast, or scribed timing marks on the gears... I call the bike a '70, but I think the engine is a '68, which puts it in the era of painted marks daubed on the gear teeth. Crazy! I finally got around to pulling the cam today, it checks out, stock, correct for the engine. So, maybe incorrect pushrods are causing the problem. Honestly, when I built the engine there was a boxful of pushrods, they all appeared identical except in the matter of cleanliness. I picked out the best looking ones. Apparently they're interchangeable from the early V7 up to the 850-T, with the exception of the early V7 Sport. Thanks for the photos and for offering to make parts available. I'll give an update if I find out anything interesting.

 

[Billiam]

Unbelievable! I went out to eyeball my cam gear for the hundredth time, put it under an arc light and inspected it with my glasses off, and found the remains of the original painted timing marks. What's more, what I thought was just a spot of corrosion on the crank gear turned out to be a witness mark where the paint mark used to be. There is one tiny fleck of paint clinging to one of the teeth.

 

[Raven]

I see what looks like a tiny paint tick but see no other marks. Was your timing correct or not?

 

[Billiam]

The black and white photo helps with the contrast a little, but even looking straight at the real thing the marks are very faint. The engine is not yet back together. When I pulled the cam I discovered a bad lifter which I overlooked somehow, so I'm going to fix that up. I think the reason why the timing was off after I set it initially was that the marked flywheel I used isn't original to the engine. According to Guzziology, some of the early 750's had only the paint on the gears and the marks on the generator pulley and timing cover, timing them from a later marked flywheel yields incorrect results.

 

[Amboman]

The black and white photo helps with the contrast a little, but even looking straight at the real thing the marks are very faint. The engine is not yet back together. When I pulled the cam I discovered a bad lifter which I overlooked somehow, so I'm going to fix that up. I think the reason why the timing was off after I set it initially was that the marked flywheel I used isn't original to the engine. According to Guzziology, some of the early 750's had only the paint on the gears and the marks on the generator pulley and timing cover, timing them from a later marked flywheel yields incorrect results.

All of the early gear driven cam V700, Ambassador and Eldorado engines only had paint marks on the gears and notches on the crankshaft belt pulley. The only mark on the flywheel was an arrow that was used to align the flywheel at TDC during assembly. It wasn't until the chain driven cam Eldos that there were stamped marks on the sprockets, but still no marks on the flywheel, only notches on the crankshaft belt pulley.

 

[fireflyr]

Billiam, I couldn’t figure out how to attach pic to message, so here’s the cam and lifters.

The gear still has the paint mark. I will scribe it too Incase the paint flakes off.