pschrauber

I would suggest laser welding, that will insure that there is no thermal issue, the laser will only melt up what is in need. I have had done that to the cylinder and cylinder head of one of my bikes too and there was no warp issue at all. As this technoloy is now at hand I would use it, laser welding has spread and thus cost are not as high as a couple of years ago.

Double ignition is also possible and some still think that it will do something to the better, and you still can get double ignition systems from VAPE in Czech for example. A double iginition and plug for wone cylinder would make sense with big bore engines, and there are some big V8 and V2 engines with nearly 1l cpacity in one cylinder, But with the Bultaco you don't have that big diamater bore so you will not have any surplus power, what you can archive is a longerr working ignition if the engine is running on the rich side just to survive and not seizing. Two stroke engines running much castor oil and super high rpm are prune to kill their plugs, as plugs don't like too rich mixture and fail easily then, with a double plug you can archive a longer life time in racing, so if one plug is failing the bike will still get a spark. Bultaco Pursangs come into my mind, too Pursangs being used for Super Moto and Bultaco Street Racer.

One for the start, one for running the engine, That was common back then, so a hotter plug to start with and a colder for running, but this was more related to racing engines. Back then you often had decomressors, (I btw. like them very much), and when these units failed with the time (where not tight anymore) most people mounted a second plug instead to mount a new one as it is not so easy anymore to get the right ones, (I dno't mention the chainsaw decompressor units instead these with cables and Hand Lever).

Well, may be it's partly the carb and then most likely the jets and nozzels which where replaced by wrong elements or in wrong sizes. A worn out carb can also be the case,especially the body which is too the cylinder and the slide, but that takes quite an effort or a wormn slide that has been used too long and rattled beside hiomself the cylinder too to oval shape ... Can you tell us please your carb set up: - slide number (on the bottom of the slide inprinted), - needle, and needle position, - needle nozzle, - idle jet, - main jet, - float valve number - choke jet, I personal would recommend a NGK BP 5ES too...

The upper coil which is for the ignition looks to have some corrosion, would be an explanation that it did cut out when getting hot. Look up the wire lines which go up to the ignition here can be an issue too, to my Aprilia the wires where laid so bad the got burnt to the cylinder. 1,5 half turn out is much to the lean side, if you turn out the carb is adjusted leaner, if you turn in richer. Please try out if the bike runs better with a different set up, when it is warm adjust the idle a bit higher, then slowly turn the screw in and out to the point where the engine uns with even higher rpm then before while idling. That is the perfect adjustment. You can then turn down the idle to normal set up you like.

Sounds interesting, and yes you can get advantages by using flat slide carbs. One step further is the use of SmartCarbs or Lectrons which have an even bigger effect, I have now mounted two SC, one on my Panda (first one) and due to the great experience now also on my Smilla and I'am very pleased and will never ever turn back, best benefit is that you don't have to adjust anything beside idle or if you want to play with engine behavior with the rod screw to get crisper or modarate/slower power output. Costs are a different thing, you can get two and a half brand new Dell'Ortos for one SmartCarb without preparation to get the unit fit to your bike, on the other Hand not to hassle with jets during the year or in different locations is a great Benefit.

The rebuild is nice but now the gas tank is an issue. That is one reason I don't do too much to the outer appearance, the patina can be nice or a burden if you can't apply the newish finish to all parts.

The swing arm axle is the most negleted bearing togethter with the steereing steam. While the steering steam is in a secure position the swing arm axle isn't an has to deal with water and dirt. I personal recommend to maintain all bearings to swing arm axle, and rear suspension at least on bikes with bearings at the swing axle and especially to air cooled monos once a year (also very importand to Montesa Cota 242 and 330 twinshock models an the following models for example)*. Which includes to clean the bearings, instrall new o-Rings and to apply new waterproof grease. That helps a lot to keep everything Sound. * especially the bearings of older air cooled monos or mentioned Montesa Cota models have only limited seal here it is very imported to do the maintaince.

It should have been a Dell'orto model: Type: PHBH 26 BS main jet: 88 needle jet: BN266 needle: X5, 2nd notch, idle jet: 48mm Gap at the slide: 4mm, gas valve is normally: 200 and choke us normally: 65 For first TX311 model from 1986, taken from German Trialsport Magazin, issue 120, March 1986.

Oven with most heat you can adjust is a good way as aluminium is expanding three times as much as steel already 250 deg might leaving the item inside for at least half an hour to one hour will do the job. Aluminium also transfers the heat so well this makes it so difficult to heat up just areas, if you heat up everything it works much better and will also not lead to any wraping!

Here is one available: https://www.offroadracing-pilz.de/Teile-Shop-fuer-GasGas/ARTIKELLISTE-ERSATZTEILE-ZUBEHOeR-FUeR-GASGAS-NACH-ALPHABET/S/Schalter-Kombischalter-HS1-fuer-GasGas::10765.html Time period Right is a Marathon of asking Dealers if they have them still in the inventory or if they know someone that might still have them, that is they way I traced them so far.

That thingy is difficult to trace but not impossible be prepared to pay around 100 - 150€ for that lights / flash lights / horn / engine stall combo! Very period correct if colorful, there are new ones just in black available for the same price range! I have them on my bikes too: See on the Aprilia and the Montesa and on the Bultaco, (no near Image, the ones on the Montesa and Aprilia where mounted from the beginning on the one for the Bultaco where back then mounted by the German importer because we needes to have a different switch, the original Bultaco was back then not sufficient):

You might ask Wayne Weedon at wayne @ fdos-design.com

Shouldn't a Saracen use a Sachs engine ... ? With a good Sachs engine I would be interested but that japanese fourstroke is a bit away from a Saracen I think.

Do it carefully without damaging the rubber or overstretching the inner enforcement, also if you have a tire workshop near by let it be done on a tire machine then as often as you want. In my experience it does not change much, I did this a couple times back in the days, but experienced not much noticeable change in grip. I do believe that the most important knobbys are the ones at the sides which then dig in when they get load also the middle knobbies which do the same.and for this one sharp edge is better then two a bit rounded. Thus I don't change anymore, I also have my bikes road registered thus they get checked periodically and you don't want to show up for checking road worthiness having tires mounted against the arrow of direction very bad idea ..

I bought the piston for my TR34 from Wössner in Germany, I gave them the used one so they could fabricate a custom replica. Wössner did then also the coating of the cylinder all in all it was then very priceworthey. The piston came with upper piston pin, roller bearing, piston pin clips and piston rings. Wössner does cylinder coating only if they can reproduce the piston too!

To me it sounds that some of the incast electronic items are beginning to failing, that is something that happens especially to electronic ignitions when they get older. I had this issue with SEM and with Motoplat ignitions which could be solved by replacing the electronic parts. Or you buy a brand new one, powerdynamo have one when I remember right.

I would enhance diameter of the tube to around 25 - 30mm, then a holetube connection between them, then I would fill up with void with insulation for two stroke exhaust. Close the box again but as such that it is easy to take apart for cleaning and replace the insulation. Then you should have a bit better performance without more noise, much more effect would have a bigger exhaust volume in general..

On Bultaco ignitions, the spark should be a super bright flash! Try to locate the timing with a multimeter with inbuild "beep" for connection and disconnection of wires, then use a mm gauge for finding OT and measuring distance of spark before OT. That is IMHO the easiest way to check the right triming. You want to check too the distance of the points which should be precisely 0,4mm, more then 0,1mm off and the ignition can fail to deliver spark.

Bultacos are a way more reliable then Montesas, Montesas have issues here and there. Ossa's do well if once rebuild properly, but to get the parts is a problem, while Bultaco parts are easy to get, second best is Montesa. Try to get a runner wich is in very orignial state, These are best, even if a bit more expensive you pay around 4 times as much for a replacement spare part then to a part bolted to or on a bike!

And no the answewr to the silde repair, I would suggest to try out to use metal kned which has the properties of Aluminium. ToDo: 1. clean the slide, 2. the Surface where you want to apply have to be rough, (Dremel) 3. clean the surfaces again from any oil, 4. kned the two component of the metacl kned, 5. allpy where in need, 6. mill and grind away excessive material, (the properties are like aluminium). Brand: https://www.ebay.de/i/302159123726

Parts for bing carbs have got very difficult to get that is true! And I know your dilemma, have gone through that by myself, what I did was get i functional Bing and a second replacemnet with better habits (Dell'Orto PHBH) for riding, now I can go back to the route of the original path in need. If you are interested I can give you (via PM) a ressource for Bing carbs which can sell you a new slide or even a brand new Bing carb either from German production (expensive) or made under licence in Spain with 28mm, albeit the last ones have the fuel supply on the "wrong" side other than that 100% original. There are guys in Germany that make slide out of brass to the Bing carbs of their twinshock Enduros and MX bikes here with enhanced design for better air flow and too to have more weight as more weight the slide have as less flutter will happen.I can proviode you with their adresses too, but that production will take time ... Last not Least the mentioned 28 or 26mm Dell'Orto even wih Malossi transparent plastic bowl is time correct, with 26mm the bike rides very good, with 28mm more agressive. Announcement of te Malosse plastic bowl in 1981 (mounted on a Dell'Orto PHBH):

Yes very important, thus there are special rubbers for the bolt with angeled surfaces to follow the tank distributed from Bultaco, you should get them through InMotion or other Bultaco spare parts distributer.

The hard chromed stanchions with a slight grind have the best properties depending sticktion, smoothness, beeing gas and oil tight, durability and lubricating the seals. The same system is used to ecxcavators and their hydraulics. The slightly grinded surface of a fresh cromed stanchion offers an oil film which gives the mentioned advantages. With the time the stanchions get "polished" and will loose the oil film thus have more sticktion, will wear the seals faster and is not as tight. Thus I personal recommend steel stanchions with hardchrome and a slightly grinded surface over aluminium ones with fancy coating and chemical etching. My supplier since 2012: Wissing Hartchrome

Four things comes in mind: - carb proper adjusted with the right jets. - after the engines smells burned are may be the crank seals not proper sitting thus gear oil get burned. - ignition is set correctly, - less oil 1:50 is very good and sufficient, then oil with low burning point, also best fuel you can get with as little as possible ethanol. Depending how you ride you might go to a hotter plug as the engine might not produce as much heat you neet to start the self cleaning process, thus I would recommend to try a hotter plug (carefully), I have had great experiences with hotter plugs (going down from NGK BP 5 ES to NGK BP 4 ES to my Sherpa and my SWM TL.NW) which now work proper for years while the colder plugs had to replace frequently, the named NGK is too without internal resistor which helps too.