11 replies to this topic

[mcman56]

I'm planning to put a Bultaco rear wheel on a C15. I also have the swingarm and am wondering if it may be a better idea to install that also. From what I read, the C15 arm has limited tire clearance and is improved if made longer by an inch. C15 type mounts could be welded to the front of the Bultaco arm to accomplish both. Has anyone done this? Are there other recommendations?

[Nigel Dabster]

mcman56, on Dec 7 2009, 07:07 PM, said:

I'm planning to put a Bultaco rear wheel on a C15. I also have the swingarm and am wondering if it may be a better idea to install that also. From what I read, the C15 arm has limited tire clearance and is improved if made longer by an inch. C15 type mounts could be welded to the front of the Bultaco arm to accomplish both. Has anyone done this? Are there other recommendations?

The bultaco rear isn't anything special is there no alternative for you?

[Woody]

I've just had a Bultaco rear wheel rebuilt to fit in my C15.

I have the standard swingarm fitted, can't see that it has ever been widened as it looks the same dimensionally as a spare I have. Yes, it's tight on clearance but it's never caused me a problem. If you fit a chainguard it won't clog the final drive with mud. Can't comment on lengthening the swingarm as mine isn't. Depends on other frame mods really as to what affect that would have.

The wheel is the type fitted to the '75 onwards Sherpa (model 159) All I did was machine back the boss (or whatever you call it) from the brake plate where it sits against the swingarm as the sprocket has to sit very close to the swingarm for chain alignment. Leaving the boss as standard pushed the sprocket too far away. I think the Bultaco spindle fits straight into the C15 swingarm spindle slots and I don't think I had to alter the standard wheel offset to centre the wheel in the C15 arm.

[mcman56]

Thanks. It sounds like I should give the C15 arm a try. However, it does have some cross holes approximately in the middle of the arm. It looks like someone had used them to mount passenger pegs. Should the arm be strong enough to tolerate the extra holes? The Bultaco parts I have are from a '71 Alpina. I thought for sure the arm would be lighter but it is not.

[B40RT]

I would repair them personally, even just for piece of mind.

[Woody]

mcman56, on Dec 8 2009, 02:23 PM, said:

Thanks. It sounds like I should give the C15 arm a try. However, it does have some cross holes approximately in the middle of the arm. It looks like someone had used them to mount passenger pegs. Should the arm be strong enough to tolerate the extra holes? The Bultaco parts I have are from a '71 Alpina. I thought for sure the arm would be lighter but it is not.

Can't comment about the strength of your swingarm now that it has been modified as I wouldn't know, but as regards the rear wheel, the one out of the 71 Alpina will be different from the one I used so what I did to get chain and rim alignment may not necessarily work with your wheel. It shouldn't be too different but you'll need to check.

The Bultaco frames up to mid '72 were quite heavy as they only began using lighter materials from that point.

[mcman56]

On the subject of swingarms....removing the swingarm pivot (7/8" round thing) on this bike requires a hydraulic press. It is very tight and makes nasty groaning sounds as it is pressed in and out. I thought maybe something was bent but it is tight all of the way through and the pressure marks around the pivot are fairly symmetric. I'm thinking of using a brake cylinder hone or reamer to open the hole but how loose is too loose. Are there any recommendations on this? Thanks

[Beamish Owners Club]

Before you go to the trouble and expense of putting a Bultaco wheel and swing arm in the back end of your Pre65 bike, I would sheck the rules of where you intend to ride it unless you intend to fide it as a twinshock rather than a classic Pre65.

[mcman56]

I'm in the process of fitting the '71 Alpina rear wheel to the C15. It looks like all it needs is some appropriately sized spacers. However, I'm not sure what to use for reference. Sighting down the sprockets makes it look close but I suspect there is a better way. Measuring the wheels...center of tire to sprocket looks similar on both. Any suggestions? Thanks!!

[B40RT]

Got to B&Q, find a bit of steel chanel, place on front and back sprockets, gives fairly accurate line.

http://www.diy.com/diy/jsp/bq/nav.jsp?acti...;isSearch=false

[mcman56]

Woody,

What are you using for a brake pedal? It looks like I could use the original BSA or with a little work fit the Bultaco pedal. Thanks

[Woody]

I cut up a Sammy Miller brake pedal to get it to fit. There isn't much room on the left side of the bike due to the bulbous clutch casing and it's difficult to get the pedal tucked in out of the way on the standard C15 frame because of that.

I very rarely use the back brake though so most of the time the pedal isn't fitted