Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board Firebird Scrambler - Working to finish up

Lannis,
I have pulled a stud to get a motor in but unfortunately don't remember what bike it was on. Don't like to do it especially if the stud is in real tight. I replaced all the studs with bolts on my B50 so I could get the head off with the motor in the frame. I went to all that trouble and have never had to remove the head again.


You might try the oil pressure mod I used on my A65. It is listed above and really easy to do, Ten years later it still has great oil pressure according to the new owner. I might have one of those little OPRV's I used. It's free for the asking.

Mr Mike

You may be able to buy some wiggle room by removing the cylinder head studs, , fit them loose in the head, offer it up , then use double nuts on the studs to seat them home.

This is supposed to be encouraging comments. Hopefully it comes out right. It's just that it's reassuring to know I'm not the only one that gets stopped dead on my projects for who knows what reason. Glad to see you've gotten yours started again. (Now maybe I'll do something about one of my projects.)

I agree 100% with this. That stud may be red loctited in there and 300 deg of heat will soften the glue so the stud can turn easily.

Gents -

Thanks for the Propane wrench advice, it worked. When I heat up something, I have the torch or heat gun in one hand, and an infrared thermomter in the other to make sure I'm not doing something stupid. I had pulled pretty hard on the double nuts, and my mechanical sympathy said that I was within a few inch-pounds of tearing out the threads on the pulling nuts.

Got out the propane torch. Playing the flame on the boss into which the stud screws, I got it up to 234 degF after a while - of course, heat is flowing away into the rest of the head as fast as the torch can input it, but at 234 I tried the wrench again, pulled as hard as I dared, and it came out like a fairy.

With that stud out, you could stand a foot away and toss the head on the cylinder and it would go on. Bolted in the head, and decided to go ahead and re-install the stud, knowing that if the head has to come off again, the stud will have to come back out. Next time, I will have a thread insert and a bolt ready; steel studs screwing in and out of aluminum threads isn't a formula for long-term success.

Lannis

Do yourself a big favour and fit a bolt instead of the stud. If you have a lathe, you could make one with a deeper head which will aid removal another time. I would also have helicoiled that post.

That's good advice, but if I keep on doing myself favors on this bike, I'll never get it back on the road. I started out pulling the top end to fix a piston slap, then pulled the motor and stripped the frame to reweld the side stand lug, then did some rewiring, then decided to buy a new chain guard and rear fender to replace the cracked originals.... And the stud screwed back in smooth and tight, so the threads aren't buggered, so it's It'll Be Right, Mate this time around....

Lannis

At least use some copper anti seize paste on the threads, they should come out easier next time.

On my A65 Firebird, I replaced the studs with stainless socket caps and helecoiled the threads, so the head is easily installed and helicoils ensure they can be tightened without fear of stripping.h

OOOHHH bloomin heathan

Reinstalled the pushrods and rocker arms this evening, after all these years I've never acquired the knack of quickly and gracefully feeding the rocker arms shafts through the left outer boss, the thrust washer, the left rocker arm, the spring washer, the thrust washer, the center boss, the thrust washer, the right rocker arm, the spring washer, the thrust washer, and the right outer boss.

Now that I've written it down, no wonder the shafts take 15 minutes each to install.

Lannis

I think it’s a dexterity thing. 10 years ago I could fit them much quicker than I can now. I seem to drop one of the washers down behind a valve spring quite often now taking more time.

Yes, my little magnet on a stick came into play several times....

I don't remember having to pry the valves open about .050" to slip the pushrods in place, even with the adjusters removed and cam in the right place, though.

Lannis

Cleaning and rebuilding the carbs, using new Stay Up floats even though the old white plastic ones were still floating, there's a limit as to how far I want to push a piece of plastic that's been marinating in gasoline for 54 years .... !

Cleaning up some of the wiring, installing a proper in-line fuse holder rather than just a blade fuse between two female terminals, found the proper 3/8 x 1-7/8 x 26 TPI bolt for the bottom rear shock mount, replacing all the worm-gear hose clamps with oetiker clamps.

Time for one more parts order if I need it before the TSMR, if I find out I'm missing something!

Lannis

Finished up the carbs this evening. Made a little fixture and rigged up some tubing to set the float height; just fixtured the bare float bowl into a vise, leveled it, put the float and needle in place, gravity-fed fuel into the banjo until the valve sealed, and measured the height of the fuel level from the top of the float bowl.

The specs say .21" +- .04 from the top of the float bowl to the top of the fuel level. So I set that for both carbs (you can bend the tabs on the newer floats, unlike the old ones where you had to heat the bowl and drift the valve seat up or down).

But when I put the bowls onto the carb bodies, I realized that the standard gasket is .040", which means that when the bowl is bolted on, the fuel level will still be .21" from the top of the bowl, but spaced down from the jet by the .040" thickness of the gasket. Does the .21" spec take account of the gasket thickness when determining how far the jet will be immersed into the fuel? Never have thought about it before .....

Lannis

I'd think it extremely unlikely that nobody at AMAL would have thought to allow for the gasket thickness in all the years they've recommended measuring from "...the top edge of the float bowl".

My bigger question has always been "do you take the angle of the carbs into consideration"? You measured in a vise, but some people do this on the bike, where the fuel level is higher at the front of the bowl than the rear. Then, what about the center stand? Front wheel down or rear wheel down? And finally, the new premier carbs don't recommend setting the float height at all; why not?

That's to say, there are so many variable and everyone reads the guidance a bit differently. I would assume that the margin for error would be greater than the thickness of the gasket, but I can't say for sure (assuming +-.04 is set low to ensure the end user gets within the true margin)

Meanwhile, the two premier carbs I purchased came with floats sitting at two different levels (visually, didn't measure) and I've never set them due to the recommendations from AMAL.

Do you have a reference for that recommendation?

From what I've read from L.A.B. and kommando, the fuel level is critical relative to the main jet, so you measure at the middle of the bowl, front to back axis.

Well, I measured it at the middle of the bowl with the float bowl level front to back and side to side. If I tilt the bowl to (about, via eyball) the angle that it will bolt onto the head when the bike is going down the road, that measurement doesn't change at that point.

So I think I'll just go with it the AMAL time-honored measurement, and not try to second-guess what the fuel level might be doing as the bike leans, or goes over bumps, or moves around under acceleration or braking. I need to go back and read (at my leisure) the past discussion and explanation that I remember that John Healy has done regarding the effect of fuel level on mixture. I understand hydrostatics to some degree, but it's hard to imagine (although I believe it's true) that a few thousandth change in fuel level will materially affect the rate at which intake vacuum will suck fuel up the jet. I better get my physics books back out. Meanwhile I think I'm "close enough". Besides that, I'm using my "go/no go" gauges to verify the .106" dimension on my installed needle jet, so that's something ....

Lannis

That go no go gauge will serve you more help than anything else.

Lannis,
I did the same thing as you with carbs in a vice to set float height. Honestly, I found that float height is not as critical as some make it out to be. It's job is to keep the bowl full of fuel w/o flooding the engine. You can run the bowl nearly dry before the engine sputters.

I once had the float stick open out on the road.. Pulled the bowl off alongside the road and the float was full of gas. I put it back together, turned on the fuel till gas came out the tickler hole, shut off the fuel and ran till it sputtered, then turned the fuel back on. Made it all the way home repeating the procedure many times and the bike did just fine.
Mr Mike

The actuaal height is not as important as both being the SAME height or you will never get them to sync .

I've officially had my fill of AMAL carbs.

Lannis

Lannis et all: The thickness of the AMAL 622/073 float bowl gasket as originally supplied by IMI AMAL, and now supplied by Burlen, is 9mm (.035"). Inlet angle for MK1 1/2 and MKII carburetors is limited to 15°. Any more than that and you need to move the pilot jet position.

The original Concentric MK1 was designed and jetted for use on two stroke engines. This led to the development of the MK1 4 stroke version. It is important to understand which instrument you have when buying and tuning your bike. A 4 stroke condition kit was made available (622/235 - new needle jet (622/122-.106), new needle jet (622/124 - 2 ring needle) and 622/128 main jet holder).

Then along comes the after market where people were having parts made wherever.
Needle jets were under, or oversize (A .106 would measure anything from .104" (or less) to .109" (or more). The 622/128 threaded hole for the needle jet was not counter bored properly and when the jet was tightened it would crush the orifice of the internal jet and close up the orifice. The air bleed on the hex portion of the 4 stroke needle jet, which should be .035", was not properly sized or deburred after drilling. Small variations in the orfice dimension makes a big difference while the straight portion of the needle is still in the needle jet's orifice.

In the early 1990's when Barry Johnston retired, IMI transfered the AMAL license to Grosvenor Works. Grosvenor already had a working relationship, being one of their outside suppliers who manufactured parts AMAL Series carbs and Bunsen burners. David Holder (Velocette Motorcycle Company) helped them finance the production of pre-MK1 carburetors including the Monobloc. At the same time (early 1990's) the UK government banned the product that was used to glue the top of the white float to the cup body. This put a whole lot of production carbs and spare parts on distributor and dealer's shelves. Before Burlen took over the distribution of AMAL products another run of white plastic floats were made. This time the product to bond the two plastic parts together worked and the floats didn't sink from leaking fuel. Both of the latest standard 622/079 (shallow) and 622/196 (deep) floats work as originally designed: they don't sink. It is interesting to know that Kenny Dreer found that on his VR880 Norton, with MKII Amals, they ran better with the 622/196 deep float.
As a carburetor, the MKI and MKII are very easy to tune. I find that typically anyone who cannot get an AMAL to tune will have the same problem tuning other brands. And don't forget that anything that changes the air velocity in the carb's venturi will change the air fuel mixture. Change in carb with different diameter venturi (going from a 930 (30mm) to 932 (32mm); modifications to port intake diameter; changes to cam timing; changes to cylinder bore diameter; ai intake leaks; changes to exhaust system's type: (pipe diameter, length of system, muffler, straight pipes, megaphone, etc.) condition of the rings and there ability to pull a vacuum; etc.. Failing to understand that the air and fuel orifices are not just a hole but react to all of the principles that make them jets as is the straight diameter of the needle (.0985").
And coming to the understanding that you MUST know which fuel circuit is in play to analize where your problem with the CARBURETOR (not all of the other things that effect Bernoulli's principles). Mark the throttle that is illustrated in a Mikuni manual. And remember that the jetting for each stage overlaps, and many flow charts illustrate how a Mikuni is tuned where the tip of the needle DOES NOT clear the needle jet.
While in some cases the fuel level in the bowl can effect performance it is usually not that critical. It is more important that the float bowl screws are not over tightened and causing an air leak in the fuel transport drilling in the float bowl gasket surface!!!!!!
Now back to work getting orders out!

We've gotten a lot of good advice over the years on tuning MkI Concentrics. I can usually get them to run like I want. I have the plug gauges for the jets, I know how to set the float level, I know how the pilot jet, the needle jet, the slide cutaway, the needle position, and the main jet interact at various throttle openings, and can recognize surging, popping on decel, blubbering on acceleration, how to use the choke to determine if jet size is off, I know how to set each side with a plug wire pulled to tune a twin like two singles, I can use two sticks to sync the carbs ...

But I get tired of the cheap cheese-like material that they're made of, and I hate that weak split ring that the Concentrics use to hold the needle in the slide, not like that robust clip that the Monoblocs used.

I took the two 928 carbs off the Firebird 8 years ago when I took it down for a top end job and a few other things. Just bagged them and laid them on the shelf. Left the slides on the cables and bagged them in a plastic baggie on the bike.

When I went to clean, rebuild, and assemble them this past week, the slides would not go down the bores. I had not bolted up the carbs and distorted them, I had cleaned them up nicely, put new Stay-Up floats in, set the float level, replaced all the soft bits, checked for jet wear and gently screwed the float bowls back on. But when I went to check the slides for play in the bore, they would NOT go into the bores without more force than I was prepared to use.

These were #3 slides that I had been running for some years. I want the bike up next week, and had no time for new slides, sleeving bores, etc. So I got out the (stock) #2.5 slides that I had, and they would BARELY go through the bores with a push.

So I spend the next two hours with a tube of Prussian blue, a big pair of Channel-Locks, and a bare slide, and squeezed and checked and massaged the bores until the slides moved freely. It's amazing how weak that carb body metal is. As I gradually got them round, I could put the slide in the bore and it would stick. I could barely touch the body with the pliers and the slide would drop ... pretty soon I could do it with my fingers.

If I find out that the Norton's problem (quit on the road on me last fall) is one of the carbs, I'm going to bin both of them and go to a single Mikuni. Dynodave, I know that your philosopy is "Learn how to fix your motorcycle so it runs right rather than buy your way out of it" and that's a good philosophy, BUT I'm getting too old to learn to get to be a world expert on a carburetor rather than riding my bike.....

Lannis

I upgraded the wiring a bit. All grounds (headlight, taillight, Boyer, Tympanium, Dyna-Coil) now run to a single point 4 inches from the battery positive terminal, and a fuse in that. I thought I'd done a good job when I took it apart documenting how I did my wiring (for example, I'd forgotten that I'd run wires from battery negative straight to a pair of relays in the headlight bucket for the high and low beams), but I didn't, and had to dope it out again with an ohmmeter. New AGM battery.

The cylinder head that went on it was not the same one that came off, so I spent several hours today refitting the exhaust. The Firebird high pipes have to go in together, and bolt together in two places, and if the header pipe won't go ALL the way into the exhaust port, the holes don't line up. So I spent time with a Dremel tool cleaing up the exhaust ports, and trying and retrying the header fit. Finally got it to a nice tight fit and the bolt holes lined up.

But because the positioning was a little different, the H-pipe and rear silencer mounts didn't line up any more, so more bending and adjusting and I need some different bolts now, luckily they're hardware store items and I can get them tomorrow.

All First World problems, it's not like I have to figure out what to eat tomorrow or go hungry, but still ... you want to do a good job and have a bike to ride!

It's just that things seem to take forever sometimes, like nothing works the first time around.

Lannis