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Classic, Vintage & Veteran For Coventry and Meriden Models. Anything pre-Hinckley goes.

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Old 11-13-2012, 05:37 PM   #1 (permalink)
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750 140v Bobber advice please

Morning all!

I have a hard tailed 1977 T140v 750cc Triumph. It has twin Mikunis and the original head.

This is set up for speed and consequently really tricky to tune, which is not what I want from this urban cruising bike. I am thinking of exchanging the head for a single carb unit and running a single carb, such as a new Amal or Wassall.

Any advice on what sort of head I need? Plus, any tips greatly appreciated.

Cheers,

Richo


Last edited by RICHO; 11-13-2012 at 05:57 PM.
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Old 11-13-2012, 05:56 PM   #2 (permalink)
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A '73-onward TR7 head will fit,but I can't see why you are having a problem.

What size are your Mikuni carbs?Where they ever jetted right?
If they were jetted to run properly,it should only be a case of a adjusting the idle speed and synchronizing the throttle cables.
If the idle and cables are adjusted,it should run as sweetly as any single-carb engine.
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Old 11-13-2012, 06:01 PM   #3 (permalink)
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Originally Posted by Mr.Pete View Post
A '73-onward TR7 head will fit,but I can't see why you are having a problem.

What size are your Mikuni carbs?Where they ever jetted right?
If they were jetted to run properly,it should only be a case of a adjusting the idle speed and synchronizing the throttle cables.
If the idle and cables are adjusted,it should run as sweetly as any single-carb engine.
Have uploaded a photo (with great difficulty, Flickr doesnt want to play).

The needles are at the richest setting, air screws are around 1 and 1/4 turns out and they are relatively well synched.

Need choke to start under any condition and need choke to run for around 10 minutes, but will not rev, only potter along. Stalls without throttle assistance. Once warm >20 minutes, will idle at ~800rpm quite happily.

I'd prefer a tickling method than dicking around with the enricher/choke method.
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Old 11-13-2012, 06:12 PM   #4 (permalink)
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The mainfold stub-out and the Mikuni intake should not touch each other or 'icing' can happen.

Most Mikuni kits come with a cheap radiator hose to join the two, and last's about one year if lucky.

Took a while to get this right on my bike- used 1-3/4" long rubber hose for automotive gas-tank filler, had to buy 4 feet but also had to buy an 18$ tool to cut it off flush.

Different kits came with different manifold stubs.

Just some thoughts- agree with Mr Pete as to "it should run as sweetly as any single-carb engine."

Quote:
Stalls without throttle assistance.
You should not be using throttle with enrichners on- see the Mikuni manual!



Have some rubber left- send me the lenght you need and will cut to suit- only need postage $ and good to go!
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Last edited by Morris the Cat; 11-13-2012 at 06:22 PM.
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Old 11-13-2012, 06:26 PM   #5 (permalink)
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Thanks for this.

1) What is icing?

2) Where should they be joined?

3) Dont have a manual.

Cheers,

Richo


Quote:
Originally Posted by Morris the Cat View Post
The mainfold stub-out and the Mikuni intake should not touch each other or 'icing' can happen.

Most Mikuni kits come with a cheap radiator hose to join the two, and last's about one year if lucky.

Took a while to get this right on my bike- used 1-3/4" long rubber hose for automotive gas-tank filler, had to buy 4 feet but also had to buy an 18$ tool to cut it off flush.

Different kits came with different manifold stubs.

Just some thoughts- agree with Mr Pete as to "it should run as sweetly as any single-carb engine."



You should not be using throttle with enrichners on- see the Mikuni manual!



Have some rubber left- send me the lenght you need and will cut to suit- only need postage $ and good to go!

Last edited by RICHO; 11-13-2012 at 06:29 PM.
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Old 11-15-2012, 01:04 AM   #6 (permalink)
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Quote:
Originally Posted by RICHO View Post
Thanks for this.

1) What is icing?

2) Where should they be joined?

3) Dont have a manual.

Cheers,

Richo

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Old 11-15-2012, 06:23 AM   #7 (permalink)
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http://classicbike.biz/Triumph/Repai...hop-Manual.pdf

this won't help with the Miks but you shouldn't consider ripping the head off a bike and changing it if you don't have a manual to set it up as is correctly. Otherwise you'll end up with a possible "custom problem" where help is even harder.

The carb manifolds should be linlked by a sealed hose. is your ok?
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