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I slightly demaged one of the two threads used on the inlet camshaft for mounting the sprocket.

To fix this problem I have purchased a second hand camshaft together with its caps (same bike model, same year, perfectly compatible). Attached some snapshots of the healthy spare canshaft that I could use

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I am concerned that mounting a used camshaft from another bike might not be a good idea. I have heard people saying that, since camshafts, caps and cylinder heads are machined together with very stringent tolerances, you should not swap these items with used ones from other vehicles.

MY QUESTIONS:

  1. Is it ok to mount a second hand camshaft from another bike on my engine?
  2. If it is ok, should I use the caps from my bike or the ones that came with the spare camshaft?

My motorcycle is a YAMAHA TDM 850 from 1998 with 85.000 km (app. 50.000 miles).

I momentarely fixed the problem by applying some thread lock (being the thread still somewhat usable and the torque only 12 Nm, it worked) but I do not think it is safe and I want to fix the problem properly (I am not riding this bike).

The easiest thing to do for me would be to swap the shaft with another one if it wont demage the engine. I believe there must be some truth in the DO NOT SWAP CAMSHAFTS motto but how much?

I see other two ways to fix the issue if swapping camshafts is not viable:

  • Repair the thread using an elicoil or a timesert (which is better). The problem would be that the depth of this thread is quite short (the bolt is 0.18 inches or 4.6mm, the thread is definetely less than 0.24 inches or 6.1mm, I guess about 0.20 inches or 5mm), see snapshots below.
  • Redo the thread. This would need to weld some material first into the hole, drill a new hole and tap it... I should find professional able to do it but I live in a rural area in Italy...

Any of these is viable given the little material available for the repair?

Many thanks

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  • Welcome to Motor Vehicle Maintenance & Repair!
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Mar 19, 2020 at 21:18

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If the camshaft is good then use it. I would consider making sure the bearing surfaces are free from dirt, oil residue etc

But the caps should be the ones from your engine as they are usually line bored to match - taking the ones from the other engine could cause serious problems.

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  • @jwh20 - No ... if you use new caps you need to have the new caps fitted. The caps act as the bearing which the cam journal rides on. These journals are fit by machining. The new cap would not be the same shape as the head portion (other half of the "bearing"). If you tried to just install new caps without doing this (as well as used caps from somewhere else), most likely you'd destroy the cam, the heads, and the new caps in short order.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Mar 20, 2020 at 13:10
  • Not really relevant to this question, though. I've deleted my earlier comments.
    – jwh20
    Commented Mar 20, 2020 at 16:00

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