sherpa325

Resin and glass mat are relatively cheap and I assume you are retired so you have the time to do a thorough repair job. Just remember not to use any fuel with ethanol in it.

Pretty sure the !59 came with 5 1/2 chrome bars. The 199 came with black steel bars without a brace and the 199A came with black steel bars with a brace

A friend dropped his bike with a missing steering stop. He damaged the outside of the tank where the tripple clamp hit it but worse still he holed the inside of the tank where it was forced onto the coil.

The shorter of the two spacers is the standard one that sits on top of the spring, I made my own some time ago, so I can't remember the exact length, maybe 20 - 25mm. Again I am unsure of the original length of a std spring but it was discussed some time ago

I just use standard springs with extra preload spacers [inmotion have them] with 180cc ATF. I weigh 79kgs so if you're heavier you may need a heavier spring.

That's just plain crazy, doesn't fit the criteria.

A friend of mine who has older bikes with fibreglass tanks as well as a newer bike, drains his fuel tank after every ride at the event. This would certainly limit the amount of time ethanol based fuel was in the tank, assuming you can't buy ethanol free fuel.

I had one of these and loved it. however it in your case it sounds like it needs a decoke. If there is a sufficient build up of 'carbon' deposited on the piston and combustion chamber it will increase the compression ratio and as the bike gets hot the symptoms get much worse causing the problem you described, Just drain the coolant take the head off and clean the top of the piston and the combustion chamber. The bigger bore bikes are more susceptible to this problem as they tend to run hotter anyway and the compression ratio and cooling system are pretty much right on the limit.

It's been my experience that back in the 70's & 80's using leaded fuel and ratios of 25-30/ 1 there was very little build up of muck in the exhaust and basically no deposits on top of the piston or combustion chamber evident during rebuilds. Fast forward to unleaded fuel and the build up of deposits in the exhaust and engine begin to occur. Around 2000 we were using Avgas with great results and little or no deposit build up. As it is difficult to get Avgas here we have been using pump unleaded and the deposits are back and they occur using semi synthetic oil or fully synthetic. I to have been told to use semi synthetic as the fully synthetic is designed for full throttle applications and is not as suitable for trials as the semi - synthetic. I run at 80/1 semi-synthetic and still get grunge in the exhaust and deposits on the piston and combustion chamber. I don't have the technical know-how to back up these results, its just what I have experienced over a number of years. The other thing about the unleaded fuel is that I find it difficult to get good plug readings as well whereas back in the leaded days this wasn't a problem and I'm talking the same bikes and same jetting 40yrs later. Cheers Greg

I would say either the 159 or 199B would be better than the original 199A. All the factory bikes used the 159 style so it sort of is period correct and they have the advantage of being a fair bit narrower than the std one and the side panels don't fall off either. Cheers Greg

Like lineaway said the 4RT in my opinion doesn't do anything better than a two stroke and I just find them more difficult to ride than a two stroke.I find it much easier to get traction and get the power down on my 300 gasser than the 4RT, however the 4RT does have good ergonomics and nice suspension but is also noticeably heavier. As a side note, as an observer of fellow riders/competitors in my class and other classes I don't see to many riders improving when they swap to the 4RT. Anyway these are just my opinions and you should really try them all yourself.Another factor that you should consider is what is the dealer backup like in your area. The Gas Gas dealer here in Australia is sensational and is a major factor in people choosing that brand out here, a phone call/text one day sees the part at your doorstep within two days max, in addition to over the phone assistance as well as the same service at events. Cheers Greg

I reckon 1/8"[3mm?] is quite thin. My aftermarket brackets are 4mm and the rear part of the mounting bracket on my GasGas is 5mm. I think you will definitely need some bracing /gusseting in behind where it's not visible.I was riding with a mate a few months ago when he noticed a scraping/rubbing noise when the bike was moving, it turned out to be a bent footrest mount [late model Sherco] We went back to the cars and basically levered it back into position with a tyre lever with a large shifting spanner on the end of it. The bike hadn't been crashed, bashed etc however he is a big solid guy 6'2" and the bracket had just bent under his weight, he is a pretty aggressive rider though. Cheers Greg

It may seem like overkill but it really doesn't take that much time to do. I have done the last three or so bikes this way and it beats trying to clamp, tack, remove, tack again, check measurements, straighten etc.

An easy way to ensure you have both pegs in the same position is to drill a 6mm hole in the centre of the purchased peg bracket and then drill and tap a 6mm thread in the frame or the support you have welded on. You can then obviously bolt the bracket on and rotate the bracket to ensure the pegs are horizontal, it saves trying to G Clamp the bracket in place, then tack weld it, then adjust etc etc, which can be very tedious . This may sound like a lot of work but it guarantees both pegs are in exactly the same position, no guess work, before final welding. Cheers Greg

The thing to remember here is that these bikes were designed by riders that were the best in the world at that point in time [Mick Andrews]. So he and other factory riders would have spent numerous days testing footpeg positions. All design work is a compromise and you rarely get anything for free. Moving the pegs forward will make the front end heavy and moving them back will make the front light and more than likely push the front forwards in tight turns but at the same time improving rear traction. Lowering the pegs and fitting new wide style pegs is one of those situations where in my opinion there are no downsides, ie you get something for nothing, the bike is more stable, riding position is improved, its all good if you can keep your feet away from the rocks. My advice would be to keep the original position forward/back lower them as far as is practical and fit some good quality pegs that have washers that allow you to move them forward or back in the mounts thus giving you some room for fiddling. I am not sure where the fad for moving pegs back has come from as the bikes now have far superior tyres than were available in the 70's, so rear traction is much better without moving the pegs back and compromising the steering. All modern bikes would have their pegs mounted a good bit further forward than a traditional twinshock Cheers Greg

Definitely a Miller frame, as was explained in an earlier post there is a photo/advertisement of a Miller Bultaco frame with the rear loop removed on page 40 of 'Spanish Trials Bikes' [Don Morley]

Hi they are about 50mm long and 8mm dia. They bottom out on the middle of the fork tube just above the bottom triple clamp. Cheers Greg

What you have is galvanic corrosion which occurs when you have two dissimilar metals ,steel [valve] and aluminum [rim] in an environment that supports corrosion [water plus tyre lube] . Depending on where the metals appear on the Electrochemical Series, will determine which metal corrodes. In this case aluminum is higher on the list than steel and will therefore lose electrons[corrode] to the steel. Its the same theory that is used to chrome plate steel, only its done in a controlled manner. Galvanized steel is another example, Zinc is deposited onto the steel and will always lose electrons to the steel [even when in contact with water] as zinc is higher on the series than steel . I would guess that any product that is used to put the tyre on should be checked to see what they contain, any product with salt in it will only assist the corrosion. The problem seems to be worse when the rims are anodised [that is colouring the naturally occuring oxide layer on the aluminum rim] The rims seem to corrode from the inside out which would indicate that the Anodised outer layer has a different electrochemical position than the rim itself. Cheers Greg

The engine is basically the same as the 199, however the gearbox has different internal ratios to the 199. You will have to run 11/46 sprockets as opposed to 11/39[standard 199A] or 13/46 [standard 199]. If you put a 39 tooth rear sprocket on the bike, first gear would be like taking off in second gear, not so good for trials riding. The ratios were changed from 199 on to give a higher fifth gear for road use. All other ratios are effectively the same with the correct sprockets. Cheers Greg

The engine number and frame number start with the model number of the bike JB 199xxxxxx A [frame no for model 199A] JM 199XXXXX A [engine no for 199A] Cheers Greg

Maybe the fact that a World Championship has been decided by a volunteers interpretation of the non stop rule may cause the FIM to do something. You can't ride modern sections, particularly at the world championship level, without hoping the bike and after watching the facebook live feeds as well as the various youtube videos this year I am pretty sure you could five nearly every rider on most of the clips I have seen, if you were pedantic.The observer and rider are more concerned if they are going to be pinged for stopping rather than they are about cleaning the section.I for one would be reluctant to be an observer in a world round, with any decision you make regarding this crazy rule being subject to scrutiny by the Rider, Team, Officials, and the Public and that's before someone puts it on youtube.The stop/nonstop is way too difficult to police with consistency, and observers have different levels of tolerance as to what they will allow, its a crazy situation to have for a World Championship. The old 90 second stop rule was way better for everyone concerned.I really feel sorry for everyone involved in this, the observer, Toby and Matteo

Back in the 70's when these bikes came out it was impossible here in Australia anyway to buy different weight/viscosity fork oils, so everyone that I knew used ATF - 180cc. If the fork topped out [clunked when doing a wheelie] just add another 10cc until it stopped. I have tried the newer fork oils in my Bultacos and I feel they are too light for forks built in that period, so I just continue to use 180cc ATF with no problems. I am very fussy about the setup of my bikes and for example I use 2.5 weight in my 300 Gas Gas as the current forks are sensitive to the modern fork oils. Cheers Greg

I was pretty sure the Montesa one fitted , off the 348/349 [30mm]

I am pretty sure all Dellortos are a fuel screw not an air screw, winding in leans it and winding out richens, the opposite of a Keihin or Mikuni. There are actually three Dellorto trials carbies- PHBH 26mm or 28mm[large body]- PHBL 26mm largest [small body] and the VHST [D or flatslide] and its the one that's difficult to keep in tune. The PHBL & PHBH are quite good carbies and require very little adjustment once set up correctly, most people changing the pilot jet to get the feel they like. Cheers Greg