Chief Carb

My 1947 Chief has an m44 carb and the one I just rebuilt has an M41. Is there a radical difference in these carbs? I have this bike starting fair, but I'm wondering if there is a problem with the carb. I can start it fine but the fellow that owns it is 78 yrs old, and I need it to start well. Its a .020 over with 80" flywheels, web cam reground cams, and relieved heads for piston clearance...seems to run rich at low speed, but the thing doesn't start now without the choke, and is set to run its best. Any suggestions? is this carb basically right?,...I wish this guy lived on a steep hill..jb

Boogs
Chief linkert carbs last 2 digits refer to the year the carb was first used, apparently the m341 was only on the 1941 chief since there is also a M341-1 and M342, both share the same specs as the M344.

Under the '80' supplement (for part# reference):
87020- 46-48 standard
285002- 46-48 Bonneville
285003- 50-51 "
285004- 52-53 "

M-341 carb: hole 1 #66 (.033), hole 2 #53 (.0595), slot width .009", venturi- 1 1/16"

M-344: hole 1 #66, hole 2 #53, slot width .015", venturi 1 1/16"

M-Bonn: hole 1 #70 (.028), hole 2 #55 (.052), slot width .009", venturi 1 1/8"

M-Bonn-1: hole 1 #70, hole 2 #51 (.067), slot .020", venturi 1 1/8"

Parts book shows 2 different nozzles: 601002-Bonneville, 102628- standard.

Jerry Hatfields Indian restoration guide list for 1950- M350, 1951- M351, 53-52- M352
I can't find any specs as of yet but it appears that slot width is going to be one of the determining factors along with the holes at each end of the slot.

I'm wondering if the M-Bonn and M-Bonn-1 are actually the M350 and M351

Hope this helps. Cotton oughta have some specs.

HOOT

M-41 is typically H-D 41 solo. M-44? Never heard of it.

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That's why I went for the trditional numbering for the Injun carbs.

Sounds like the evil manifold leak to me, Boog!

PS: I don't believe there are really any M-351 Linkerts. All of the '51s seem to have M-350s on them.

Cotton, I did for sure have an intake leak. I turned the manifold down and made some brass ferrals for it and couldn't get it to seal. I then made teflon ferrels for it, They sealed like crazy, but if you rode it ten miles the nuts were loose. I finally found some good brass and made another set, this time not only with a smaller OD, but longer, They have passed your test to the point of lifting the valves off the seat with no leaks. I know this thing has a little throttle shaft wear, but it doesn't react to spray. The engine returns to idle quickly but still isn't exact. This cam was ground to Stark specs I was told. It may be a little low on vaccum at idle. I do know this thing will get to 75 MPH in a heartbeat. I'm clutching at straws to make it more dependable. Cold it starts w/2 primer kicks with the fuel and choke on, then set choke back halfway turn on ignition and Varoom. But if you miss it you may kick five minutes. Cotten I made a leak tester to your specs just for this thing, now I use it on everything.

Panic, I was wrong as you know, it was an M 344.

Thanks folks.

Digging around in my parts I've come up with an aluminum manifold that looks identical to the other one. What years were the aluminum manifolds used?

Only things I can think of to watch for:
1. internally vented venturi (notch on leading bottom edge)
2. nozzle looks like this, bottom is Chief 74, top is Bonneville (holes are .052"):


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[This message has been edited by panic (edited 09 April 2002).]

Boog!
The aluminum manifolds were later, like '48 on. They REALLY distort and wear baadly.

I tried teflon years ago and discovered quickly that it extrudes. That's why I finally turned to PEEK for my Liberty Rings.

If we have eliminated the manifold leaks, and have dismissed any floatlevel concern, or even daylight around the OD of the venturi, then any other tuning problem usually involves throttleplate wear into the body of the carb. (The only fix I know is to hone the body for an oversize plate and venturi.)

Well, now I am totally confused, the engine is 80" with Kiwi wheels,rods, and pistons, modified 74" heads. The engine has regular 74" valve lifts and reground 74" cams with less duration than the Bonneville, what nozzle do I want?

Cotten, I wish I had thought of it when I was making that last set of ferals and I would have cut an oring groove to seal against the cylinder. I cleaned up the face of the spigot with a sanding block & fine file. If there is a leak it is not showing. This bike runs and starts better every time it's ridden, I guess I just need to go put about 500 mi on it, it only has about 150 now. If it were mine I would be OK with it as is, but I need for it to start easy for the owner. I can't wait to get started on an engine just like it for mine.

Why not try out your M344 on it just for a reference point. With the differing slots and holes between the 2 carbs you should get a difference in starting and low rpm running.

The nozzles that Panic shows. As the rpms get higher the more holes will be uncovered on the nozzles admitting air in with the fuel being pulled up through the nozzle. The larger the holes the more air admitted along with the fuel making a leaner mixture. Looks like the Chief needs less fuel than the Bonneville at the upper rpms.

So if this engine/cam combination has the Chief nozzle and it's plug checks are okay at all rpms, it's okay. If upper rpm is too lean, Bonny nozzle. You should notice by having to change highspeed needle adjustment for different rpms or slightly closing the choke.

HOOT

Problem solved, The guy that owned it came over today and started it cold and hot, rode it about ten miles and pronounced it too goood! I'll let him put some miles on it and check it again. When they are breaking in it seems they change every time they are ridden. I would feel better if he would quit riding it 25 mph in high gear though. Oh well, I guess ya gotta let go sometimes..jb

Reminds me of one time when I got down to the Brit shop. The owner had spent the whole day before trying to get an early 60's 500cc BMW to run better after putting new plugs and points in it. He was all frustrated, told me to see if I could solve it's running problem. Perfect compression, put fresh gas in it, no air leaks, cleaned and synced the carbs. Crack the throttle open and you just had to wait for the rpm's to slowly build up. We were both so totally disgusted with how poor it ran that we decided to let the owner run it up the road. We had spent 2 days trying everything to make it run better and had resigned ourselves to telling the customer 'no charge' after he got back....and when he did.... he said it never ran that good in all the years that he'd owned it. Found out that BMW flywheels are extremely heavy and don't respond to rpm changes very rapidly.

HOOT

[This message has been edited by HOOTER (edited 10 April 2002).]

Hooter:
BMW owners are just as strange as the machinery. Ten or fifteen years ago one of my little brothers friends brought a old R69 in and wanted a tuneup. After checking it out I told him that it had low compression on one cylinder and almost no compression on the other. He screamed and cussed at me because BMWs never need overhauling before 100,000 miles. He called a few weeks later and cussed me again because the dealer just tuned it up.This made me doubt my diagnosis untill the mext time I saw my little brother who brought me the bill from the dealer which said tuneup but included two pistons, rings and labor to install them. But just said tuneup so he could still brag that it went 100,000 without a overhaul.
Dusty

Yer right Dusty
Cheapest bastards on the motorcycling scene I've ever met. Had to argue all up and down with one idiot about his heads. The exhaust guides were so wore that the guide hole was totally oval shaped (like a 1/4 mile flattrack from 10,000 feet), and the exhaust valve seats were eroded bad. He had just gotten the heads done the year before at some bigtime national BMW outfit, installing unleaded seats. Me? I don't compromise, just told him to send it back to them or pay me to install parts that I know will work. Retorqued the heads at a 1000 and it's been a few years so far with no problems. He stops in for a compression and leakdown test (for free) and seems still leery about my work, cause I never did a beemer topend before, so how could my work and parts selection last longer than the major national super duper bigtime outfits ultimate big fix. Too bad, I guess

More power to ya Dusty

HOOT

Almost forgot
I wouldn't ever want to sit on sompthin' at a stoplight that, when idling, would waggle my butt.

[This message has been edited by HOOTER (edited 11 April 2002).]