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 Posted: 07-20-2017 08:03 pm
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Jim Ketcham
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I am having a problem on a new 2.2l conversion where the circlip on the aux. housing shaft that holds the timing belt gear slips back out of the groove after a few hours of operation. I have replaced the circlip with a spare and the problem reoccurred. Visual examination of the groove as compared to one on a spare shaft does not reveal any issues. The cam and aux. shaft gears are new htd gears from Lotus Bits. Belt appears to ride nicely in the middle of the cam gears and engine runs great. Has anybody experienced this problem? I am thinking of pinning the gear to the shaft to keep it from riding back. Am I treating a symptom or solving a poor design issue? I have done 2 other 2.2 conversions and have never experienced this problem.

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 Posted: 07-21-2017 05:23 pm
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redracer
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Some of the aftermarket cam wheels did not have a chamfer on at least one of the hole to "capture" the circlip. Hopefully the other side of the wheel does or else you will need to have one put on or send it back to the seller for chamfering.

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 Posted: 07-21-2017 06:50 pm
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Esprit2
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Jim,
The Auxiliary pulley is to be mounted with Loctite, and it should require the heat of a propane or MAPP gas torch to remove it. I've not seen this written in Lotus manuals, but I've found Loctite in many factory-virgin Lotus 9XX engines I've taken apart.

The little wire circlip is not a very solid abutment, with or without the chamfer in the pulley. If the pulley doesn't over-ride the circlip, then it can at least become loose to the point that it can wobble back-n-forth against the Woodruf key in response to engine power pulses. I've had three aux pulleys wear the keyway until it was over 0.50" wide in the middle (yes, half an inch or more). Viewed from either side, the ends of the keyway looked normal. But remove it and look into the bore, and the keyway was very wide.

I first experienced this on a 907 engine I had rebuilt, but had not used Loctite on the Aux pulley. It was having ignitiion timing issues... it was jumping all over the place. I'd re-set the static timing, and it would change again in very short order. It was a long witch-hunt that drove me nuts until it finally ended with the discovery of the worn, wide keyway. Replacing the aux pulley solved the ignition-scatter problem. But the problem returned in less than a year, because I didn't use Loctite... again. The next pulley went on with Loctite, and the problem never returned. Given the amount of surface area in the pulley bore, Blue Threadlocker will suffice.

By the way, if the Woodruf key is off to the side in the wide notch, then it's locked in behind the normal narrow width end of the slot. That was another mystery that really complicated pulling the sprocket off the aux shaft.

It was after that experience that I started to notice that Auxiliary pulleys on Lotus 9XX engines were Loctited on, and required heat to remove. For threads, Blue Loctite doesn't require heat. But the pulley is aluminum, and trying to pull a Loctited pulley off without heat will often result in distortion of the spokes, or fracture. Heat it up until you see bubbling at the joint line between the shaft and bore.

The cam pulleys are clamped firmly against a solid shoulder, they don't get loose, and they don't experience that keyway wear problem. Only Auxiliary pulleys clamped against the little circlip get loose.

Cam pulleys should be installed with Anti-Seize.

Auxiliary pulleys should be installed with Loctite. Just the bore... avoid getting it in the keyway in either the bore or the shaft.

*~*~*~*
When using heat to remove an aux pulley, be very careful not to fry the lip seal that is right behind the pulley. Wwrap a wet rag around the stub of shaft that's exposed between the pulley and the aux housing, covering the seal. Then direct the flame or heat gun onto the hub, from the back side shooting forward.

Regards and Good Luck,
Tim Engel

Last edited on 07-21-2017 09:23 pm by Esprit2

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 Posted: 07-21-2017 07:42 pm
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Jim Ketcham
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Tim and Bruce,
I was hoping for responses from you.
Good info. I will check chamfer ( compare it to oem 907 pulley) and reassemble with loctite. I am surprised I have not bumped into this issue before. I guess I've been lucky.
Thanks for the advice.
Jim

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 Posted: 07-21-2017 09:28 pm
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Esprit2
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Apply the Loctite to the pulley bore. Maybe just a very little bit on the shaft, wiping most of it back off... ie, just a thin 'primer' to ensure the shaft is wetted. Rub it in, wipe it off.

The goal is to avoid having the pulley scrape a wave of Loctite off the shaft, and back onto the lip seal behind the pulley. Be careful, watch for it, and immediately wipe off any ooze that does occur. Don't goop the seal.

By putting a heavier application of Loctite inside the pulley bore, the shaft will scrape the excess forward out of the front of the bore, away from the seal. Wipe off any excess prior to installing the special washer and retaining bolt.

Regards,
Tim Engel

Last edited on 07-21-2017 09:32 pm by Esprit2

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