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MR4-A Carb

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Chuck Sumner

Post Tue Jul 14, 2009 12:07 am

MR4-A Carb

I have a MR4-A carb that I would like to put on a 46 UL bobber, that I have. It doesn't have idle or power needles. What will work on it? As I said, its a bobber and doesnt have to be correct, just work. Also, what manifold will adapt to the UL, to mount the carb? Thanks for any info.
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panic

Post Tue Jul 14, 2009 7:59 am

Re: MR4-A Carb

If you're not fairly well versed on the Linkert you won't like the results.
I'm not sure the needle tapers match anything else, but the late (M61, 53, 74) body is probably close enough to try.
All the low speed circuits are way too rich, the main nozzle fuel curve is completely wrong.
There is only 1 4 bolt manifold available (1940-65? WLDR, WR, K, KH, KR), and needs quite a bit of work to your cylinders to adapt.
This offers almost no increase in flow over the far more common, cheap (and better suited) M74B.

Summary: don't.
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Beachdog

Posts: 765

Joined: Mon Oct 16, 2000 12:01 am

Location: CA USA

Post Tue Jul 14, 2009 9:26 am

Re: MR4-A Carb

Listen to Panic. Don't. Sell the MR4A to a racer for $1000, and buy yourself a cool carb for the street. If you must run a 4 bolt linkert on your BTSV make an adaptor plate from 3/8" stock and work the transition with a die grinder so it has no ledge. You won't be happy with a chokeless race linkert on the street.
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VPH-D

Posts: 43

Joined: Fri Jan 18, 2008 2:24 pm

Post Tue Jul 14, 2009 12:45 pm

Re: MR4-A Carb

Will a K model 4 bolt manifold fit a BTSV ?
VPH-D
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panic

Post Tue Jul 14, 2009 1:44 pm

Re: MR4-A Carb

Does anyone here see WHY I delete my posts?

Why bother - answer a question, and the very next thing to appear is...

the same question.
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Chuck Sumner

Post Tue Jul 14, 2009 2:03 pm

Re: MR4-A Carb

Who wants it? Its got a brass bowl, not aluminum
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MarkBranst

Posts: 346

Joined: Thu Jun 24, 2004 12:01 am

Location: Champaign-Urbana, IL

Post Tue Jul 14, 2009 3:23 pm

Re: MR4-A Carb

Panic,

This would be one of the rare instances when you are absolutely dead on and justified ... but your answer would be useful to someone who actually might read it, so please don't delete.

Thanks, Mark
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RUBONE

Posts: 380

Joined: Fri Nov 30, 2007 7:24 pm

Post Tue Jul 14, 2009 5:58 pm

Re: MR4-A Carb

The reason why vintage racing has seen the disappearance of early WR and KR models is just because of what was just touched on. The comment" sell it to a racer" is total crap. Racers can't afford those prices so the racing scene has suffered greatly. The only ones paying that money are building bikes that will never see the road again. Trailer queens, faux racers, bragging trophies, but not RACERS! :evil: Every one wants to have that perfect WR, or 2-CAM, or KR to show off but never to use. You should be ashamed of yourselves! Motorcycles, including RACERS, were built to ride. Not collect and wank over! And that is my rant...
Robbie
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Beachdog

Posts: 765

Joined: Mon Oct 16, 2000 12:01 am

Location: CA USA

Post Tue Jul 14, 2009 6:36 pm

Re: MR4-A Carb

Robbie,
Didn't set out to ruffle anyones feathers. My comment referred to what the market seems to be for that carb. I bought my first WR in 1969 for much less than what that MR4A will bring today. I can't afford these high prices either. I would bash about on a WR with $1000 invested in it, but we all start to think twice when we see what these racers and parts bring today.
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Pa

Site Admin

Posts: 4692

Joined: Sun Mar 12, 2000 1:01 am

Location: Ohio USA

Post Tue Jul 14, 2009 6:42 pm

Re: MR4-A Carb

Robbie....I had the same mindset of those trailer queens for years. Wanted to build the perfect restoration. I've had a change of heart over the years though. I still strive for perfect restorations but they will be ridden. And my circle of friends will ride them as well. Can't take em with me, heh ? But what if I spill em ? Comes a fearful question. Shit happens...I will say. :wink:
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panic

Post Wed Jul 15, 2009 9:19 am

Re: MR4-A Carb

The price remark was innocent and harmless.
The market price is, and has always been, set by the most improvident, foolish and impractical dilettante, rather than the serious enthusiast or even investor (as the stock market has demonstrated).
Those who feel injured by $1,000 price tags on carburetors are prisoners of their own egos, not of market forces. It's not a loaf of bread, and you don't need it - you only think you do.
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Chuck Sumner

Post Fri Jul 17, 2009 6:18 pm

Re: MR4-A Carb

Found the correct needles on e-bay. After reading posts, think I will keep it and put on the bobber I am building. Got no problem pulling aircleaner cover and hand choking to start. This wont be a everyday rider, got a 1940 UH , a 1961 pan and a 1967 shovel for that.
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panic

Post Sat Jul 18, 2009 9:19 am

Re: MR4-A Carb

All the low speed circuits are way too rich, the main nozzle fuel curve is completely wrong.

I'm not sure you understand what's involved in correcting this. It's not an adjustment or a replaceable part - it's permanent surgery.
You're going to be inventing a main nozzle that never existed before, and the complexity of this circuit has driven Weber owners to sell their carburetors.

A "tickler", similar to the spring-loaded float-submerging pin as found on the Amals, can be adapted as a cold start assist.
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Chuck Sumner

Post Sat Jul 18, 2009 10:36 pm

Re: MR4-A Carb

Guess this is my last post, due to the fact, some are nasty comment, foul use of words ya all. I am not a ignorant fool. I ask for advice, not to be belittled.

No need for it to be your last post. Belittlement was not their intentions. Lighten up Bro. Their true intent was to help. Pa
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46WL

Posts: 45

Joined: Fri Nov 10, 2006 10:09 am

Location: Midwest

Post Sat Jul 18, 2009 11:49 pm

Re: MR4-A Carb

I'm interested in your carb. email me larsonbe@hotmail.com
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panic

Post Sun Jul 19, 2009 9:17 am

Re: MR4-A Carb

I'm delighted to hear that your expertise on the Linkert is so well established.
Perhaps you might share with us exactly how you intend to modify the main nozzle, which nozzle you think best as a donor, and why?
How you intend to modify the idle hole?
The transition hole?
The throttle disc angle?
The air correction circuit?

Always happy to learn from an expert.
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Chris Haynes

Posts: 2628

Joined: Wed Jul 05, 2000 12:01 am

Location: Los Angeles, CA

Post Sun Jul 19, 2009 9:22 am

Re: MR4-A Carb

Chuck Sumner wrote:Guess this is my last post, due to the fact, some are pompus blowhards, Fuck ya all. I am not a ignorant fool. I ask for advice, not to be belittled.



It sounds like you are being given sound advice. Don't be so stubborn( I know that is hard for a Texan :D). Listen to the guys who know this stuff.
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panic

Post Sun Jul 19, 2009 10:43 am

Re: MR4-A Carb

Were the "correct needles on e-bay" these: http://tinyurl.com/ltq8u7
("Linkert M53, M53A1, MR3 , MR4, MR4A High Spd Needle", advertised as "This is the CORRECT needle ( copied from an original NOS item ) for the M53,M53A1,MR3,MR4,MR4A carbs, straight venturi or bombsight versions, high speed side. Also used in various racing versions.")?

The 27297-52 replica they're selling is evidently not the same as the MR-4 27300-46R, used 1946 until at least 1954 - why would the factory change it, since the M53 was already in use?

But you already knew that...
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Pa

Site Admin

Posts: 4692

Joined: Sun Mar 12, 2000 1:01 am

Location: Ohio USA

Post Sun Jul 19, 2009 4:49 pm

Re: MR4-A Carb

panic wrote:I'm delighted to hear that your expertise on the Linkert is so well established.
Perhaps you might share with us exactly how you intend to modify the main nozzle, which nozzle you think best as a donor, and why?
How you intend to modify the idle hole?
The transition hole?
The throttle disc angle?
The air correction circuit?

Always happy to learn from an expert.


Panic....I really think he thought he was receiving an insult. Pa
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panic

Post Sun Jul 19, 2009 9:55 pm

Re: MR4-A Carb

On the topic of needles: that same vendor sells many replicas, but it looks like their research is a bit sketchy - they think the M36 and M45 nozzles are the same, 1-1/4 and 1-1/2" needles are the same, etc.
If you buy something from them I'd at least get a specific answer so you can either return it or complain.

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