Triumphrat

DIRTRIDER01

To all you Triumph officianodos out there, I have just begun a rebuild of a 76 triumphh t140. Upon opening the engine cases I have discovered a nasty little circumstance. It would appear that the drive gear for the tach has broken, in the process, the bike began to eat itself. What I would like to know is if my case is junk or if I can simply clean up the inside of the recess and eventually rebuild. The housing for the tach drive still threads in tightly. Pix are of the inside of the exhaust cam recess where the tach drive gear inserts and the end of the exhaust cam itself. Any info will be greatly appreciated. Thanks- guy with a very long project ahead

DAGAD

Hi Dirtrider, no real problem there. Replace the bushes for the camshafts. While they are out, deburr the 'nasty' end in the crankcase and press in new bushes, you will need to heat the cases BEFORE driving in the new bushes. You can replace the thimble in the end of the exhaust cam part# 70-9988 TACHOMETER DRIVE PLUG.
To remove the old bushes, I use a 7/8" unc tap ( might be 3/4"..... can't just remember), make a thread in the bush. I have a 7/8" (3/4?)bolt made into a slide hammer, screw in the bolt and draw them out. To fit the new ones, use the inlet cam and a soft faced hammer.
Roy.

Mecchanica

Yep, like Dagad says....but....don't bother fixing the stock exhaust cam, just replace it with a cherry used or even new 69-72 Bonneville exhaust cam. Provides a little more lift, duration, and overlap. Use R tappets for more duration, hence torque at higher rpm but more wear, or fit STD radius tappets for more midrange punch. In conjunction with your Thruxton grind inlet cam, (STD radius tappets only) you will note a significant boost in the midrange torque. Use refaced or new tappets when you change a cam.
Remove all four stock oilite cam bushes and refit with new hard bronze cam bushes, available from Precision Machining. MAP Cycle in FL is a distributor. You will need to drill the oil holes in the timing side bushes after installation and then bolt the cases together to line ream and hone. I remove the blind (left) bushes with a 7/8 fine tap and a slide hammer with a special fitting I made....just a bolt welded to a nut that threads onto the slide hammer shaft. Email and I can send photos.

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DIRTRIDER01

Thanks guys for the info, I was a bit worried when I saw this that I would need to replace the case. Day 7 of a long project.

DAGAD

Stick at it dirtrider. Good to see you back, Kim.
Roy.