Bultaco Sherpa M190 Rebuild Finished

[trialsrfun]

Good point that Bondy 2 split links are required.

How I measure wear on a drive chain is first clean it, pull it out straight, push the links together then pull one end slowly stopping at the point where the movement reaches the far end of the chain, if there is more than 2% stretch which is roughly 2 links to the 100 then it is probably ready for replacement before it wears the sprockets.

[pschrauber]

Mmmh ... isn't it better to replace sprockets and the chain together. In my personal experience a even slightly worn sprocket will wear out a new chain quicker and vice a verse.

Then again, as a trials bike is not so powerfull in comparison to a MX or street bike the chain lasts very long when maintainced right. My personal thump of rule to chain wear is as long as I can't pull up the chain from the rear sprocket more then half of the height of the theeth from the sprocket itself everything is OK. When there is more play I replace all of them as the chain can hop over in silly accidents, (may be only a MX / Enduro problem).

To the half link's it's easy to get half links from Regina and IRIS, from other brands I really don't know??? Anyway I'am very stuck with DID ER MX chains as they are one of the few in my experience that have a good durability on big bore MX bikes too and still are light, so i use them for my KTM and also for the trials bikes. The half links I mounted to the DID chains for the trials bike I took from IRIS (as DID at least doesn't sell them were I live ??) they are very close in diameter to the shafts inside the rollers, never had a failure so far.

[d250b]

I have an RK chain and I don't seem to be able to find 1/2 links on tinternet. Maybe another make would fit but I'm inclined to just get anew one.

I assume I should remove it and count the links before ordering a new one or is there a default number for Bultacos? I was thinking that the chain certainly couldn't be old, worn and stretched when it's too tight but I suppose a link might have been removed previously??

Front sprocket is brand new as I put that on myself, went to an 11t down from the 12 that was on there. To my uneducated eye the rear one looks ok, there was an old worn one in a box of bits and it's nothing like that.

[woody]

Half links aren't available from all chain manufacturers and as someone else mentioned those that you can buy don't necessarily fit other chains, so you may not get one that fits your chain.

You should be able to push the wheel all the way forward without the brake arm fouling. What may be causing your problem is that your brake arm is from a Pursang and the way it is fitted means that it sits on an angle and so is closer to the swingarm. The Sherpa arm is straight, not bent and so has more clearance because it sits vertically, not on an angle. Try removing the arm and turning it so that the lower half points up vertically and then see if you can move the wheel further forward (obviously you'll need to disconnect the rear brake to do this but all you're trying to achieve is to see whether the arm position is stopping the wheel going fully forward)

Or you could fit a longer torque arm which will lift the spline above the swingarm as it will rotate the brake plate anti-clockwise

I've found with standard sprocket sizes, especially on the later bikes which are 11:39, the chain is always too long or short to get proper adjustment. I run non standard rear sprocket sizes which helps get the chain adjusted properly (ie: if you had one or two teeth less on your rear sprocket the chain wouldn't be so tight) So sprocket sizes are another way of overcoming a chain that won't adjust properly. Yours are 11:46 standard. If you fitted a 45 for example, the chain would be less tensioned and it wouldn't affect your gearing noticeably. Depends on how you find the gearing you have as to whether you'd want to change. Your rear sprocket looks a little bigger than 46 but hard to tell.

What fuel tank have you fitted? Fibreglass, plastic, alloy?

Edited September 2, 2014 by woody

[woody]

Brake arm is positioned like this with a longer torque arm

[d250b]

Thanks Woody, that bike looks superb, like the rims.

Disappointing about the brake arm because it's new and that was what I was sent as correct for the bike. I honestly did wonder because it was the only bent one I'd seen. Mine was broken at the tips and I assumed that it was a common problem and perhaps most we're replaced with later arms which were straight. I will try that tomorrow and see what happens but I will need to get that rectified anyway.

I think that would probably fix it because it doesn't need much movement at all.

From memory I'm sure it's a 46 tooth sprocket. I changed the front one because even to my uninitiated mind, first gear was just too swift and I wanted it slowed down a bit!

It's a plastic tank. Bike came with 2 plastic tanks and the one which was on it was one of the textured finish ones. Part of my dream was the way the bike looked so the proper tank decals were a must so the other one got the treatment. It was in poor shape having badly bubbled. Neighbour is a panel beater/painter and I gave him the two Ford colours mentioned on here and I'm not even sure which one it is!! It was blasted first and he said he took off about 3mm of old paint! I've done plenty reading about the dreaded ethanol so I'm fully aware of the risk but I've just started using Aspen fuel in my 2stroke machinery so I'm using this in the Bultaco. ( I'm using the 4T Aspen fuel and mixing it at 40:1) so there should be no ethanol issues but I still intend draining the tank and venting the cap just in case.

I've discovered that with the plastic tank being wider at the front, the nut which secures it hits the fork stanchion before the fork it's the steering stop on full lock. I've stuck a small foam pad on the stanchion to stop it getting damaged. Has anyone experienced this? I can't see a way around it part from maybe a half nut?

I paid for an old alloy tank at the same time but the panel beater gave me a funny look when I showed it to him! It's seen better days. He said he could sort it but I was looking at a bit of £ which by that stage I couldn't contemplate because sorting everything else had just mushroomed. So I think I will try and sell the alloy tank to recoup some money.

I'll give you an update when I move the brake arm.

Cheers

D

[bondy]

hello i had same problem with a new alloy tank the fork tube was hitting the bolt on 1 side.you can rather buy another bolt with a allen flat head or do what i did grid the hex head down but make sure you leave enough on it to get your spanner on it. or if it.s a plastic tank you can pull the neck in alot more than a alloy 1 and cut abit off thread on the bolt. another thing i did with the new alloy tank was the stock steering stops wasn't quit long enough like 2 or 3 mm so i bought some nylon bar cut to size drilled and rounded off on the blank side did the the job nice very close to the tank with out hitting it and didn't lose any lock.

[d250b]

Like the idea of the nylon bar and I see it's quite cheap on the auction site.

New brake arms are only available from inmotion in the bendy form, no straight ones at all.

Decisions, decisions.........

[bondy]

make 1 mate or if you can't do it go to a engineers they will make 1 for you.

[trialsrfun]

I have an RK chain and I don't seem to be able to find 1/2 links on tinternet. Maybe another make would fit but I'm inclined to just get anew one.

I assume I should remove it and count the links before ordering a new one or is there a default number for Bultacos? I was thinking that the chain certainly couldn't be old, worn and stretched when it's too tight but I suppose a link might have been removed previously??

Front sprocket is brand new as I put that on myself, went to an 11t down from the 12 that was on there. To my uneducated eye the rear one looks ok, there was an old worn one in a box of bits and it's nothing like that.

I have been told that the Regina 520 half link is perfectly ok and a proper fit with RK 520 chain, I have not tried this myself but am assured that it is so. Both BVM Moto and InMotion list Regina 1/2 links on their sites.

[lbhbul]

Tank front bolt hits;

Machine two alloy headed & threaded bushings of proper length, connect them with a short stud in the center of frame

Two counterbored washers $ rubber washers for each side, 6m Phillips screws.

Fasten tank in this manner, cant hit with fork leg.

Rebuild looks spectacular.

Good Luck

Larry

Edited September 16, 2014 by lbhbul

[d250b]

Thanks Larry/trialsrfun. I should have updated the post re the chain but have been really busy.

I bit the bullet and got a new chain (Regina). However, I had to remove a couple of links obviously because it was too long but this got me back to square1; in that at this new length the brake arm fouling the swing arm was again an issue. ( If I had left an extra link in I couldn't tighten it enough). The simplest way I saw to get round it was to file down the top corner of the brake arm. Only had to remove a few mm and it gave me that wee bit extra adjustment. So I guess with hindsight I could have done that with the old chain and saved myself some £!!! Oh well, as I've said its a drop in the ocean now!

Larry, I'll definitely look into your solution for the tank. I had considered lengthening the stops but that would of course cut down on the lock. I haven't looked into the half nuts idea either as I've been too busy with work.

I've used a button head Allen bolt which means that one side looks really neat and flush to the tank, I wish you could get a female Allen head "button nut" ( if you know what I mean) to go on the other side and that would look smart.

I have some alloy blank left from the new axle spacers I had made up so I will talk to my engineering guru and see what he says.

Cheers

D

[lbhbul]

d250b, Your engineering fella will understand what to do with the post, I use one inch matl. for the washers $ one half inch for the frame if my memory

is still intact,

the bolt hole thru the frame is about 10 mm, the width seems to vary from bike to bike.

Have a nice day

Larry

[woody]

The easiest and cheapest method for me is to measure how much the lock stop needs extending to stop the fork hitting the bolt. Then take off the nylon buffer, cut a piece off the shank off a 6mm (or whatever) bolt to that length and tap it down inside the buffer and refit it. The lock stop is now extended. The nylon buffers are long enough to allow a piece a few mm long and still fit properly.

The usual reasons that the forks hit the bolt is that the lockstops have been cut down or the plastic tank has spread at the front which means a longer bolt is used.

Obviously, the above method won't work if the lock stops have been cut back too far

[bondy]

thats a good way to do it as woody says. i had the same problem as i said before i bought some nylon bar cheap to buy and made them 2mm longer drilled hole to size sorted didn't loose any lock as woody said i think mine had been made shorter.