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2021/05/13 03:17:57

paulbaker1954

Tecumseh Cam gear replacement and cam timing

I have a problem I can’t figure out.

The cam gear on my Tecumseh engine stripped some teeth. The gear is a press fit on the crank and has no key way.

I have a spare crank with the same gear that I can pull off and use to replace my busted one but now my problem.

Because there is no key way I have no way of accurately knowing where to position the cam timing dimple relative to the crank.

So how will I be able to do the cam timing with effectively no aligning marks.

Here is my theory......

My thought is to install the cam with the lobes furthest away from the valve lifters with the engine at TDC on the compression stroke with the magneto magnets lined up so I know this is the firing positions.

Before anyone says get a new crank THEY ARE NO LONGER AVAILABLE.

4 comments Leave a comment

GBertolet

I imagine that one of the stripped teeth, was the one with the timing mark on it. If you are going to wing it, and guess, being off one tooth, the engine won't run, and you will have to do a teardown again. I have been there and done that.
May I suggest you go on Ebay, and do a search for your Tecumseh part number. It's amazing what you can find there. You might find some NOS parts, or take offs from parted out engines. I have rebuilt several engines that have had discontinued parts, and have always found replacements on Ebay. New items being offered all the time. Give them a try.
If you wish, you can post the part number, and I will make an attempt to help you find a replacement.

2021/05/13 11:37:08

paulbaker1954

GBertolet
I imagine that one of the stripped teeth, was the one with the timing mark on it. If you are going to wing it, and guess, being off one tooth, the engine won't run, and you will have to do a teardown again. I have been there and done that.
May I suggest you go on Ebay, and do a search for your Tecumseh part number. It's amazing what you can find there. You might find some NOS parts, or take offs from parted out engines. I have rebuilt several engines that have had discontinued parts, and have always found replacements on Ebay. New items being offered all the time. Give them a try.
If you wish, you can post the part number, and I will make an attempt to help you find a replacement.

Thanks but no the timing mark is still on one of the teeth but as the gear is broken it is free to rotate on the crank so I have no idea where the original position was. Find it a bit odd that Tecumseh made these as a press fit and not a keyed gear as I would expect.

The engine is a Tecumseh Centura 65 and these were made by Tecumseh Italy and seemed to have a different part numbering system to USA Models. The Engine is marked as CTR195 ES OHV-E-75006.

I have managed to get hold of a parts list and the crank is part number 16070124 but I have had no luck in sourcing one anywhere.

2021/05/14 03:05:05

AVB

Most crankshaft and camshaft gears all have a timing mark. Plus I have never use the crankshaft keyway to align a set of gears.

I would think even if crankshaft gear doesn't have a mark you set the piston at TDC. Just note not all engines align this way either due to configurations that don't allow the camshaft to be installed. Also flywheel magnets don't align perfectly with the ignition coils due ignition timing requirements.

Being off by one tooth camshaft wise will change the power (torque) curve of the engine.

2021/05/14 07:15:48

paulbaker1954

Sorted, managed to find a crank that had different part number but all the same dimensions. Only difference I can see is the PTO shaft has a couple of additional key ways.

I checked the shaft and journal dimensions and seem to be same as the bust one. Also stroke measures the same

Anyway it all fitted fine and engine turns over fine now it’s all back together.

2021/05/18 04:02:51

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Tecumseh Cam gear replacement and cam timing

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