1978 Triumph Bonneville

[Homeval]

 

[Homeval]

I have a knocking noise on engine deceleration which sounds like it is coming from the primary chain or clutch area all gears but seems worse in 1st. I have the cover removed and the primary chain appears to have 3/4" play, no slippage of the clutch. This bike had been stored for 2 years. Any suggestions?

 

[grandpaul]

Smart-looking bike with classic style mufflers like that.

You might want to see if you can turn or wiggle the alternator rotor at all on it's centre hub. At least dump the primary oil, remove the cover, remove the alternator stator, and give it a try.

They come loose and cause serious damage, could put an unsuspecting rider off and who knows what...

 

[Rudie]

knocking noise on engine deceleration which sounds like it is coming from the primary chain or clutch area all gears but seems worse in 1st. I have the cover removed and the primary chain appears to have 3/4" play,

In addition to checking the alternator rotor, adjust the primary chain correctly - 3/4" is excessive, it should be 1/2" from pulled-up to pushed-down; on engine deceleration, all the chain slack is in the top run, where the tensioner isn't.

You're a new owner? Be aware the bike is specifically a '78 T140E, which was an interim US-only version between the previous T140V and the '79-on T140E; it is different from both:-

. Cycle parts are the same as the T140V.

. Engine parts are the same as the T140V except for cylinder head, carburettors and crankcase venting, which are the same as the '79-on T140E.

. Electrics are (were originally) positive ground, not the '79-on T140E's negative ground. '78 T140E was also fitted originally with the same points, 12V coils, single-phase alternator and rectifier as other '78 bikes, not the '79-on T140E's original electronic ignition, 6V coils, 3-phase alternator and rectifier. The lighting toggle switch (on top of the headlamp) shell and wiring is peculiar to the '78 T140E; however, if you do ever need a new lighting switch, they are available as they were supplied by Lucas/used by Triumph on all models/versions/variants '68-'70 and '71-'74 on the 500's.

'78 T140E Owner's Manual is at http://classicbike.biz/Triumph/OwnersManuals/1970s/1978-Bonneville-750-T140E-Owners-Handbook.pdf. It contains basic maintenance instructions, including adjusting the primary chain. However, be aware the Lighting switch and wiring diagrammed are T140V, not '78 T140E.

The specific '78 T140E parts manual is "T140E 1978 Late 00-7003" available from Vintage Bike Magazine » Parts Books; however be aware it's a Supplement listing only '78 T140E-peculiar parts, anything not listed/shown in the supplement is in the parts book for all '78 bikes (also on the same site).

Workshop manual is at http://classicbike.biz/Triumph/Repair/1970s/73-78-Triumph-Bonneville-Tiger-Workshop-Manual.pdf; however, it does not contain anything '78-T140E-specific, only procedures and illustrations common to all '78 bikes.

 

[Homeval]

I have a knocking noise on engine deceleration which sounds like it is coming from the primary chain or clutch area all gears but seems worse in 1st. I have the cover removed and the primary chain appears to have 3/4" play, no slippage of the clutch. This bike had been stored for 2 years. Any suggestions?

 

[Homeval]

Thanks for the suggestions. I did pull the cover and the alternator rotor seems ok but the chain is slightly loose. This bike only has 13,000 miles on it but I am going to replace the tensioner while I have the cover off. I recently acquired this bike after it had been sitting for several years. First order was to clean out the gas tank (rust), rebuilt the carbs and replaced the fluids, plugs and points, now she starts on the first kick. The knocking noise just freaked me out since it is rather heavy and I was afraid it might be something more serious, like bearings. With the clutch disengaged the plates rattle a little, not sure about that one but no slippage or anything out of the ordinary. I will post the results when she is back together. Thanks again.

 

[Homeval]

By the way, this is the sixth Triumph I have owned, the first being a 67 Trophy when I was 18 and the last being a 1979 750 Bonneville which I foolishly sold when my son was 15 and eyeing it up. Sold it, since at that time I had little extra money and bought him a 125YZ so he could learn to ride in the dirt. Of course, I also got a 125 for myself and a trailer to pull both. Still have the trailer (shown in the picture).

 

[Homeval]

Thanks for the suggestions. I did pull the cover and the alternator rotor seems ok but the chain is slightly loose. This bike only has 13,000 miles on it but I am going to replace the tensioner while I have the cover off. I recently acquired this bike after it had been sitting for several years. First order was to clean out the gas tank (rust), rebuilt the carbs and replaced the fluids, plugs and points, now she starts on the first kick. The knocking noise just freaked me out since it is rather heavy and I was afraid it might be something more serious, like bearings. With the clutch disengaged the plates rattle a little, not sure about that one but no slippage or anything out of the ordinary. I will post the results when she is back together. Thanks again.

Still fiddling with this project. With the clutch plates removed, the center hub is out of round by about 1/8". It would appear that the main shaft of the trans is bent. Further disassembly may be necessary. The drive chain broke early on in the restoration due to my stupidity of trying to break the clutch loose by jamming it in gear with the clutch pulled in. Looks like a trans disassembly is next up. Thanks for the suggestions.

 

[Rudie]

With the clutch plates removed, the center hub is out of round by about 1/8". It would appear that the main shaft of the trans is bent.
Looks like a trans disassembly is next up.

You have to remove the clutch hub anyway. Do that and check the mainshaft taper before any more disassembly, you might find the hub was badly-fitted on the mainshaft taper.

If this was the problem, both tapers should be inspected closely for damage caused by the clutch hub being tightened in the wrong position. Also check the tapers fit with "engineers blue" to ensure they're engaging fully.

 

[Homeval]

You have to remove the clutch hub anyway. Do that and check the mainshaft taper before any more disassembly, you might find the hub was badly-fitted on the mainshaft taper.

If this was the problem, both tapers should be inspected closely for damage caused by the clutch hub being tightened in the wrong position. Also check the tapers fit with "engineers blue" to ensure they're engaging fully.

Thanks, I will try that before taking the trans apart. As I said, I really pulled a stupid when I did what I did. At least now I have the problem in sight and it is not the rod bearings or something which requires a complete tear down.

 

[Homeval]

Thanks, I will try that before taking the trans apart. As I said, I really pulled a stupid when I did what I did. At least now I have the problem in sight and it is not the rod bearings or something which requires a complete tear down. I have another bike which is my daily rider so this one is a labor of love and not a fast priority.

 

[triumph david]

H, thats a nice looking bike!!!

 

[Homeval]

Thanks. 41 years old and only 13,000 miles. she needs to look better.

 

[CarlS]

I think it looks great!

 

[Homeval]

Turns out that there were several broken gears in the transmission along with a bent mainshaft. She is fixed and shifts like new now. Now on to making the old bike look pretty.

 

[sikatri]

Excellent! Glad you figured it all out!

 

[Homeval]

Excellent! Glad you figured it all out!

Thanks for all the suggestions from members.