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#322907 - 07/14/10 3:46 am 441 top end on a b25  
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Ed Haeuser Offline
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Wisconsin
My son and I pulled a 68 b25 out of the barn. The piston was stuck so we pulled the head and knocked the piston loose. Then pulled the cylinder off and found a crack at the base of the sleeve. Still thinking it was a 250 cylinder I happened to find one on eBay that was cheap and was closing in a few minutes so I bought it. Well.......then I went out and measured the bore and it was 79mm which would be from a 441.

Is there a problem running the larger displacement with the 250 lower end. It seems that the cases are the same, but how about everything else?

Also, The header seems to be press fit into the head but I'm not sure. Is this the case? I don't want to force it if it is not.

I will be getting a manual soon but I was hoping to get this info right away.

The connecting rod bearing seems to have excessive play so it looks like a total rebuild. this will be my first BSA project.

Thanks,

Ed

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#322914 - 07/14/10 4:59 am Re: 441 top end on a b25 [Re: Ed Haeuser]  
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Bodger Offline
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Santa Barbara, Cal.
congratulations and good luck...the standard book all here recommend is the Rupert Ratio book for BSA unit singles...buy that first.

Does the B25 cylinder still fit? that might be a better idea, and more reliable as well as using standard parts.

I'm thinking of sleeving my B44 down to 350 or 250 to be more reliable, and as I never get above 25mph anymore, it's all I need.

:>

And why oh why are we still trying to convert semi reliable standard designs into unreliable hot rods, geez..what, are we still 15?

Anyway, good luck , and the other standard recommendation here is to send the whole thing to Ed V in Michigan, he's well recommended and is also a sponsor here, and posts as well.

That's all I think I know....

#322925 - 07/14/10 8:10 am Re: 441 top end on a b25 [Re: Bodger]  
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kommando Online content
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Scotland
This is a mod I have seen in the UK for trials bikes, its a 350 using the bore and stroke of the B40, as long as you have all the mods to ensure the oil pressure stays high at the big end it will work fine, in 250 form they rev'd to 8250 rpm, other than the big eend bearing everything else is std B44. EdV +1, plus he can resleeve your current barrel as the length will be non std.

Best manual is Rupert Ratios book on the Unit singles, all the oil mods are listed.

Header is press fit into head, when you come to remake it use silicon goo to ensure its gas tight.

When fitting new big end bearings use a pair of Triumph 500 shells, they are made from a better bearing material and do not have the oil bleed hole which removing retains oil pressure.

#322992 - 07/14/10 5:21 pm Re: 441 top end on a b25 [Re: kommando]  
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hh Offline
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hh  Offline
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British Columbia
Do your engine cases say "B25" or "B44?" I think someone has swapped the engine for a B44. And is your rod steel or aluminum? If aluminum, it's a B25 rod, otherwise it could be C15, B40, or B44.

The B25 case *castings* are the same, but the machining of the B44 is completely different. The spigot hole is larger to accept the 79mm bore, and the cylinder/head studs are not only larger diameter, but are farther apart. It's easier to just get some B44 cases if you're going to attempt some kind of homemade B40 special. If you want to do it yourself, you need to weld up the B25 cylinder stud holes, bore out the spigot hole, and relocate the cylinder stud centers, all four of them. Considering that cases can be purchased for around $100-$150, I don't see it being economical. If yours has been converted this way, the B25 barrel and head will no longer fit, likewise if it's a B44 engine.

I had/have been thinking about doing a similar project, using a C15G crank, which is end fed and of the latest design, and a shortened B44 barrel into B44 cases. But by the time I bought a few parts lots, I had enough to make a B44 engine, so I haven't bothered yet. The extra expenses of shortening the barrel didn't seem worth it just to lose about 100cc.


"Beer is proof that God loves us and wants us to be happy" - Benjamin Franklin
#323062 - 07/15/10 5:06 am Re: 441 top end on a b25 [Re: hh]  
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Bodger Offline
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Santa Barbara, Cal.
why not make an offset crankpin, (easy when I say it :>) or whatever you kids do these days, and destroke the B44 to 350 or 250?
You could tune for torque by selecting a rod length appropriate for your intended use, and have a more reliable , less powerful, slower wearing bike.

alright, enough stupid ideas, nitey nite.

#323073 - 07/15/10 9:08 am Re: 441 top end on a b25 [Re: Ed Haeuser]  
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Ed Haeuser Offline
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Wisconsin
Thanks everyone for the responses. I ordered the rupert book as suggested.

I am away from home for a few days, but I will measure the stroke when I get back to find out if it has the shorter 250 stroke or the longer 441 stroke. Also will check the connecting rod.

In response to one of the posts....The case and frame have matching number B25B serial numbers.

I would prefer to change it back to stock 250cc but I'm thinking that resleeving the b44 cylinder might be the most cost effective (cheapest) solution.

Thanks,

Ed

Last edited by Ed Haeuser; 07/15/10 9:09 am.
#323098 - 07/15/10 2:13 pm Re: 441 top end on a b25 [Re: Ed Haeuser]  
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hh Offline
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hh  Offline
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British Columbia
Ed, you have a very interesting machine if you have the 441 top end on the B25 bottom. If you're really interested in putting it back to the stock 250cc displacement, we should talk. I have large quantities of B25 parts. I'm still interested in doing what somebody already has done to your machine. Maybe we could trade relevant bits?

The only snag is your numbers wouldn't be matching anymore if that means a lot to you. These bikes aren't exactly highly coveted collectors' items, but they are generally worth more with matching numbers. That said, large changes to the main components, like yours has, don't increase value to the collector, only possibly a racer, if anybody is racing in a 350 and under class or something.

I'm interested for the novelty since I've owned and ridden B25s and B44s, but never a B40, and there are desirable characteristics that each has and the other doesn't. Maybe the cross has neither, I don't know. Regardless, at the very least, I'd love to see some pictures of the disassembled engine if you could put some up.


"Beer is proof that God loves us and wants us to be happy" - Benjamin Franklin
#323666 - 07/18/10 9:33 pm pics and some more data [Re: Ed Haeuser]  
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Ed Haeuser Offline
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Wisconsin
So here is the picture of the bike after a hose down. It's really in pretty decent shape. The tank has a split in the seam but it shouldn't be that hard to fix



I measured the stroke and it is 90mm which I believe is the same as the B44. It seems to me that the standard stroke for the 250 was around 70? Is that correct? If so, the PO must have put a different crank in? You can see in the following pics that the case appears to have been opened up to accept the larger piston and jug. That's as far as I am now. more to find out as It comes apart. Certainly appears to be an interesting engine. Patiently waiting for my R Ratio book.

Ed






Last edited by Ed Haeuser; 07/18/10 10:00 pm.
#323687 - 07/19/10 2:21 am Re: pics and some more data [Re: Ed Haeuser]  
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hh Offline
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British Columbia
Thanks for the pics. Your stroke is indeed correct for a B44 at 90mm, and the 250's is 70mm. I'm more inclined to believe that somebody has made a "stealth" B44 disguised as a B25 utilizing a B44 engine in its entirety, because the machining of the spigot and the chamfer look exactly like any other B44 case and I don't see any evidence of welding around the bolt holes.

Either the numbers may have been ground off and re-stamped to match the B25 frame (which is exactly the same as the B44 frame and is directly interchangeable) or a blank case was obtained and stamped. Blank cases still show up on eBay once in a while. The factory supplied them as replacements that way.

What's also unusual here is that it has the exact appearance of a 1967 B44VR. The B25s were blue instead of red.


"Beer is proof that God loves us and wants us to be happy" - Benjamin Franklin
#323696 - 07/19/10 3:31 am Re: pics and some more data [Re: hh]  
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Steve Erickson Offline
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The Northwoods... Michigan
This is a weird deal. A "stealth" B44 isn't indicated by the red color scheme, it now looks like a B44SS, not a B25. Is that red a paint job, or is it actually the original Gelcoat??... that would certainly add to the confusion.

Out of curiosity, and because it is easy to check, what is the diameter of your kickstarter shaft?

#323699 - 07/19/10 4:12 am Re: pics and some more data [Re: Steve Erickson]  
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hh Offline
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Steve, are you looking to determine the year from that info? I've got B44 cases with both sizes. By stealth, I meant in terms of its registration, certainly not look in this case.


"Beer is proof that God loves us and wants us to be happy" - Benjamin Franklin
#323701 - 07/19/10 4:24 am Re: pics and some more data [Re: Steve Erickson]  
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Ed Haeuser Offline
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Wisconsin
The tank appears to be gelcoat. I cut a slot in the seam where it leaks so I can repair it and it is red all the way through. I am attaching a picture of the serial number but I blanked out the last digit. The frame has the same number minus the Y. Does this look like a normal stamping of the number?

I will try to get the shaft measurement in the next couple of days.

Thanks to everyone for the input,

Ed


#323710 - 07/19/10 5:56 am Re: pics and some more data [Re: Ed Haeuser]  
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hh Offline
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British Columbia
I got this from another site regarding A-series BSA twins http://www.bsaownersclub.co.uk/Engine_Frame.html : "Machines re-exported in 1970 were stamped with a 'Y' suffix to indicate that they were 1970 models and therefore eligible for the increased warranty."

Maybe it applies to B25 models as well. B25B is 1968 which would jibe with that.

Also the site says: "The numbering started at the beginning of each season and always started at 00100 leaving the first 99 for experimental use. The numbers were consecutively allocated throughout a model range so as an example all B group machines were lumped together irrespective of whether they were a B25 or B44. From experience in cross-referencing machines against the factory despatch books of which the club have a copy, we have found that in about 50% of cases the bike was not despatched according to the date of the lettering. Sometimes they were despatched months earlier or later so the lettering system should just be taken as a rough guide."

This bike is really weird.


"Beer is proof that God loves us and wants us to be happy" - Benjamin Franklin
#323711 - 07/19/10 6:03 am Re: pics and some more data [Re: hh]  
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Steve Erickson Offline
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The Northwoods... Michigan
There are so many questions here, I am just trying to narrow it down a bit. If the shaft is 5/8", on what appears to be a 68 model, it would indicate to me that the lower end is truly a B25... I'm pretty sure, without having checked my references, that by 68 the B44 was using the 3/4" shaft, while the B25 was still 5/8". But it sure looks like a punched out B25, doesn't it?

Red gelcoat adds to the oddity, though it is just a few bolt on pieces. No matter how this works out, it looks like the PO had waaay too much time on his hands, put a lot of work into a conundrum.

The number stamp looks OK to me, though I certainly make no claims to being expert on this. Actually, it is a bit neater than what I'm accustomed to seeing, but the workers had to be sober once in a while, I suppose.

How does that quote go... " the good thing about Brit bikes is that so many parts are interchangeable... the bad thing about Brit bikes is that so many parts are interchangeable."

#323730 - 07/19/10 12:39 pm Re: pics and some more data [Re: Steve Erickson]  
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kommando Online content
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Scotland
That con-rod looks steel not alloy, so B44 crank in a B25 looks best option, maybe someone took the best of two B44 and B25 parts bikes and ended up with what you see here. In fact I think is is a whole B44 engine made to be a B25 with some creative stamping.

Last edited by kommando; 07/19/10 12:42 pm.
#323760 - 07/19/10 4:38 pm Re: pics and some more data [Re: kommando]  
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hh Offline
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hh  Offline
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British Columbia
The spigot hole looks way too much like a B44 case to be opened up after manufacture, unless the machinist took great pains to recreate the factory look, which is unlikely. And you'd think there would be some trace of discoloration due to the different welding wire or rod adjacent to the relocated cylinder stud holes, but there is none to be seen.

I'm 99% sure that's a B44 engine case. The engine stamping does look too straight almost, doesn't it? The Y is interesting, especially since it doesn't appear on the frame, or maybe it's obscured. Maybe they were really drunk in the factory that day and somebody grabbed a B44 engine and stamped it as a B25. That doesn't explain the red glass bits though.


"Beer is proof that God loves us and wants us to be happy" - Benjamin Franklin
#323848 - 07/20/10 2:19 am Re: pics and some more data [Re: Steve Erickson]  
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Mitch Offline
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The way I remember it there is no way a 250 case would take a B44 jug. The bottom end on the B25 was nothing to write home about anyway... the weakest part of that engine.

#323854 - 07/20/10 2:49 am Re: pics and some more data [Re: Mitch]  
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hh Offline
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hh  Offline
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As I detailed above, the 250 case will take a B44 jug since it's the same casting. It just takes some work. I've been running a 250 hard for about 7 years now almost daily and haven't had a problem with the bottom end. I run an oil filter and change the oil regularly.


"Beer is proof that God loves us and wants us to be happy" - Benjamin Franklin
#323874 - 07/20/10 9:16 am Re: pics and some more data [Re: hh]  
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BSA_WM20 Online content
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BSA_WM20  Online Content
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Sydney Australia
Don't over look the option that DPO has stamped a B44 case with B25 numbers to defraud the state on taxes.
It was ( and probably still is) quite common down here where there is a massive difference in tax from 250 to 441


Bike Beesa
Trevor
#323909 - 07/20/10 1:52 pm Re: pics and some more data [Re: BSA_WM20]  
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Steve Erickson Offline
Steve Erickson  Offline


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The Northwoods... Michigan
If there was any difference in tax on a 250 vs 441 anywhere in the US, it would have been peanuts... certainly wouldn't warrant what has been done to this bike.

I'm guessing it had something to do with maybe a rolling B25 chassis with title, and acquiring parts to complete it. But that doesn't explain the extra drillings at the crankcase mouth, or the B25 stamp on the case. And if the stamp is a fake, why add the Y to it???

#323914 - 07/20/10 2:20 pm Re: pics and some more data [Re: Steve Erickson]  
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hh Offline
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hh  Offline
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British Columbia
BSA_WM20: we already covered the topic of restamping. Where I live, it's 400cc and below, and then it costs double to insure a 401-750cc bike, so there's certainly incentive here.

Steve: what extra drillings? I don't see any.

Here's an example of unstamped B44 cases: http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=280535678558


"Beer is proof that God loves us and wants us to be happy" - Benjamin Franklin
#323917 - 07/20/10 2:34 pm Re: pics and some more data [Re: hh]  
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Rich B Online happy
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Stone Creek OH USA
hh sez:

"Machines re-exported in 1970 were stamped with a 'Y' suffix to indicate that they were 1970 models and therefore eligible for the increased warranty."

That is complete BSA mythology. The subject has been beat to death on this board.

-Y is 67 bikes and seems to indicate the revised electrical system with zener diode mount and revised alternator support on twins

Y is 70 bikes that are affected by altered warranty coverage in the States. These bikes are almost always true 70 bikes, though some do seem to be a bit of a factory bitsa as the shelves were cleared for the OIF bikes.

As far as this bike, IMO, the engine is a B44 that has been altered. Y stamped on a single is an oddity. B44's used 5/8" kick start shafts into 67. The 3/4" shaft either was a running change in 67 or started clean in 68....most likely the former. Front brake wouldn't have been a 67 B44R as they still used the 7" half width scrambles brake.


Life is too short to drink cheap, bad beer.
#323920 - 07/20/10 2:52 pm Re: pics and some more data [Re: Rich B]  
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hh Offline
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hh  Offline
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British Columbia
Rich B: I didn't say that, the BSAOC said that and I quoted it. I haven't followed the beating to death of the Y issue on this board, and I dread even thinking of trying to use this search engine to find it as I'm sure it would be completely hopeless when "BSA" returns nothing, LOL.

Are you saying that twins were sometimes stamped "-Y" or "Y" above? I don't really follow what you wrote.

The front brake looks like a 7" full width SLS. I'm not sure you can ascribe any particular feature to any particular year the way they built these things using up left over stock and with variations between home and export, but OCICBW.


"Beer is proof that God loves us and wants us to be happy" - Benjamin Franklin
#323985 - 07/20/10 10:34 pm Re: pics and some more data [Re: hh]  
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Steve Erickson Offline
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The Northwoods... Michigan
Oops hh, too many singles... I was thinking of the B50 drillings, which are different.

I think the 7" SLS was used by both B25 and B44SS for 68, so no help there.

#324034 - 07/21/10 9:14 am Re: pics and some more data [Re: hh]  
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I realise this is a massive thread drift...

HH was wondering about the suffix numbers applied to the A series twins in the lated 60's.

http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=8500&page=1

Pages of reading here

The 180 day warranty applied to all models of BSA sold retail after March 1970.

The Bulletin was issued, in part, to confirm the existence of the batch of bikes made during 1970 but numbered in a misleading sequence. All were twins and numbered with a 1967 type system. (Not at all the same though).

I am not at all sure how the info remains on the BSAOC website.. ,we have yet to see any confirmation of how it was derived. It is also completely contrary to the data contained on the BSA (USA) Bulletins.

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