Tuesday, July 22, 2014

Paint is going on...

I have not been posting much recently about the TY. I have been making progress, but the problem is that once I get into the garage I just tend to get to work instead of taking pictures and documenting what's happening. So, here's an up-date.

Painting the frame with a touch-up gun is difficult, messy and wasteful. In the future, especially if I am somewhere near a shop that can sandblast and powercoat I will go in that direction. This frame has numerous nooks and crannies which are virtually impossible to reach with a spray gun. Naturally the overspray goes everywhere. There is a lot of wasted material. Finally, in frustration I got a couple of rattlecans to finish the job. Otherwise many small tabs and mounts were not going to be adequately covered. Today I applies a couple of coats of clear to try to bring out a bit of a shine. It looks successful on the main tubes.

I have to keep reminding myself that this is a trials bike...a bit of a gentleman's trials bike..but still a trials bike. It will get very dirty and it will spend more than a little time on its side in the dirt. No sense in going crazy on the cosmetics.

The tank was significantly easier. The touch-up gun hold enough paint for two coats. So far the tank has about four coats and has only had a tiny bit of sanding in between the coats. I ordered a couple of set of decals off of ebay today which are supposed to be suitable for a middle 70's YZ...in other words, bumble bee stripes.

Once I have figured out the decals I will clear coat them. While waiting for the decals, I will check and double check the assembly of the engine and install it into the frame...then the suspension and the wheels and I will be done. Can't wait!

Just some routine maintenance...

As I mentioned in an earlier post, the old Amal has been switched for a Chinese Mikuni. Subsequently, I've attached a foam filter to keep the worst of the grime out of the carb. Now, with the new carb in place, I am riding the bike a lot more. It is nice to just sit in the saddle and explore the Baja beaches, as opposed to my usual stand-up stance on the trials bikes.

The experience is really improved by the fact that the bike now idles...what a treat, and it is significantly faster and cleaner on the top end. Anyhow, from the beginning  there has been a steady and very low volume leak from the primary case, nothing unusual for a Bultaco and actually it is comforting because it means that there is oil in the primary case. I had been adding smallish amounts of oil before each ride to insure that everything was well lubricated in there, but it was time to change the oil and conduct a little inspection.

I have to say that it is a real treat to work on a bike that has been properly looked after. The seven allen head bolts which hold the primary side cover to the case were in perfect condition. They all had washers, and they were tightened to the correct torque. Not crazy tight...but tight enough. The primary case gasket was in place and it had not been coated with gasket cement so it could be reused. And, none of the threads in the center case were stripped.

300 cc of fresh 10wt. oil and I was done. The filler plug was undamaged and the drain plug was, likewise, in perfect shape. After a quick wipe-down I was off for a short ride around the neighborhood.

Friday, July 11, 2014

Trial Fit on a Trials Bike....

The frame has been given a couple of coats of primer. I am still not happy with the look of some of the joints so there is probably some additional grinding to be done. However, this was a convenient point to trial fit the WES exhaust and the rear fender. It went together very nicely.

The various bits and pieces of the exhaust system are made of fairly soft (but thick) aluminum and so I was able to bash the required clearance in the muffler where it passes close to the shock mount and the expansion chamber itself need a few hardy whacks to clear the frame. To my eye, it appears that the muffler will just clear the rear tire at full travel.

Next I have to go to the biggest auto parts store in La Paz and see if they will let me play in their radiator hose section behind the counter. I need a piece to connect the header pipe to the expansion chamber and another piece to connect the expansion chamber to the muffler. Both of these joints are a nice tight push fit, but I want the added security of a nice rubber joint to keep the drool and vibration to a minimum. Besides, all those rubber joints remind me of my Bultacos (both in the present and the past).

This trial fit was also an opportunity to create the reinforcing rivets and aluminum sheet for the rear fender. I'll post some pictures after I have had an opportunity to grind and file a bit. Right now it looks a little rough.

Friday, July 4, 2014

A (Chinese) Mikuni for the Bultaco

As I mentioned some time ago, my 175 Campera came with a very old Amal carburetor. It really was not interested in idling and acceleration usually brought forth a lot of stumbling which took a while to clear. It started well from cold, but was entirely disinterested in starting when warm. Apparently this set-up was originally intended for a Mercurio which had a 25% larger displacement. I love the bike but the Amal was in the way.

Solutions are available. In this case I simply did an ebay search for carburetors for a DT 175 Yamaha and this little beauty turned up. The results naturally included genuine Mikuni's which were priced in the $100+ range. This one was $26.00 plus shipping. I bought two with the thought that I might want to use the second one for my TY 175. I have to admit that the machining is not up to the standard of a Japanese Mikuni and the general fit and finish is clearly one step below the original.

Mounting this carburetor to the Bultaco really was not a big deal once I figured out where to get the right pieces. There are lots of rubber mounts available to fit a Mikuni carburetor to the Amal mounts, but they are sized for the larger Mikuni's. These rubber mounts are obviously intended for the larger British Twins and Singles. The mount this carburetor to this smaller bike I had to source pieces from Speed and Sport which is a United States supplier. I would expect that these similar pieces would be available in either the UK or Australia. Below is a photo of the pieces necessary.

I had to source the nuts to make it all work. I needed two M8X1.25 machine screws to attach the alloy adapter plate to the original manifold and then two more M8X1.25 socket head bolts to attach the rubber  adapter to the alloy plate. Not overly complicated if you can figure out where to get the pieces.

One last complication with this carburetor is the longish cable guide which comes out of the top of the carburetor and is intended to guide the cable into the body. This guide is threaded but it has no mount for the throttle cable itself. If you have a lot of old carburetors around you may have a receiver for the cable guide, otherwise you are back on ebay trying to find the right words to do a search.

The final hurdle is the throttle cable itself. The cable guide is unusually long and so you will probably need to shorten the outer throttle cable a couple of inches, or you will have to make your own. In my case I got a throttle cable kit from Venthill (which is UK based, but has a U.S. distributor) and made my own. Making your own throttle cable is not easy. It is not something that can be done with a hacksaw. These cables are incredibly strong and will only yield to something mounted on a Dremel tool. One more word of advice, do not ever solder in your bare feet. Don't ask.

The carburetor completely transforms the bike. It idles, apparently forever...even on the sidestand. It accelerates cleanly and returns promptly to idle when you release the throttle. Unfortunately, it is not interested in starting...either cold or hot...so I have some work to do. Right now, I just have to squirt a little starting fluid into the carburetor and away it goes. I'll keep you informed.