woody

You don't say which Fantic wheel it is. From the 303 model range to the K-Roo they had tubeless rims that looked just like tubes rims - a tubed tyre won't necessarily seat properly on one of those. Any model prior to the 303 range had tubed rims.

Which manual - genuine Bultaco or one of the Haynes / Clymer as the latter don't always necessarily get it right. If it is the wrong jet, maybe someone tried to richen it up to compensate for an air leak at some stage - worn crank seal, worn throttle slide, or maybe they just fitted the wrong jet. As for advantage, if everything on the engine is working as it should then no, there shouldn't be any advantage to fitting a larger than standard jet.

Possibly, many of the early bikes didn't have matching numbers whereas the later ones are more likely to, so yours could have come like that or it could be another engine fitted by someone. As they are so close, it's more likely it came like that. The story is that when the engines were bench tested, the better motors were put aside for the works riders which is why there were mis-matches. No idea if this is true or not but you'd think that from the first time that was done with each new model, none of the subsequent bikes could match unless they omitted a few numbers on the frames to get them back into matching sequence....

I don't, no. Most are holed because of the kickstart stop missing. It's the kickstart that does the damage if it goes all the way round and uses the fragile magnesium casing as a stop. The casing for that engine is hard to come by. It will repair ok with metal bond etc. but make sure you have the stop fitted.

Have fun getting the motor back in the frame..... I did... You may want to try fitting the frame around the motor before fitting any other parts to it. It's awkward because there is only one rear engine mount and the swingarm spindle goes through it. It was a bit of a wrestle as I remember. I use Barnett plates in my Ossa and Bultaco and they work very well. I tried them in the Jumbo but they made no noticeable difference (why I didn't mention them) which is what led me to believe that the main problem was the actuator mechanism rather than the clutch itself

Sorry, mis-read your previous post as the Jumbo you rode had the reed block assembly fitted, not blocked off with the plate. With the reed blocking plate fitted (therefore no reeds, it's either / or) it does flatten the power off a bit at the bottom end, but not much, but it will still pull like hell when opened up. With your engine completely rebuilt and with a reed fitted, I don't think you'll find it too linear. If you do you should have been world champion... As I said, mine had the extra weight and fully retarded timing and a carb that wasn't spot on tune - it still pulled any gear you wanted and I'm 17.5 stones (250lbs over there) Understand what you mean now with matching the cases - no, nothing like that was done, it was just stripped and everything rebuilt - honestly, it doesn't need anything, but if you can do that sort of thing, I guess it won't do any harm. I repacked the exhaust on mine too, middle and tail pipe as this makes a big difference to how smooth they run. And when they are packed properly they have a superb exhaust note. The clutch is heavy, even with the extra arm under the tank. If you try to lighten it by elongating the actuator in the casing I think you have the situation where the clutch doesn't fully disengage as the lengthened arm doesn't throw the plates out far enough. If you adjust it on the centre adjuster to eliminate the drag it will then slip. The clutch action and actual bite of the plates can be juddery as well although this seems to fluctuate from bike to bike (clutch is the same as 240/280 SWM) The actuator runs on 3 ball bearings and there are 3 different sizes, so it may be worth trying other cases with the larger (12mm) diameter balls. I also found that the actuator was rubbing on the casing which didn't help things, so I ground back some of the ribbing so that it didn't catch. It is possible to get them working to your liking, just takes a bit of time and trial and error. I also tried running 2 less springs but the motor has too much power and the clutch will slip if you're trying to fire it off the clutch in 4th gear up big climbs. Best get it working with all springs in. Best twinshock there is in my opinion (but there's another one I have never tried yet, so you never know...)

Hi Scot, a model 92, also 325cc, in good fettle puts out oceans of power, pulls like a train and breathes just fine through that airbox so I can't see any reason it won't work efficiently on your bike. As long as an airbox doesn't stop the engine getting the air it needs it will work. You should see how small a KT250 airbox is but they will rev their nuts off - contradicts all this stuff about large volume being required. It's only my personal opinion, but the flow of air being unrestricted is more important than fitting the largest volume airbox possible

Rob's bike is my old bike, it has a flywheel weight fitted, not weight taken off the flywheel, there is absolutely no point or need to take weight off the flywheel Are you sure it was a Jumbo you rode? As said before, in standard form the Jumbo motor is sharp and will lift the front wheel in 4th from tickover without even trying, they are very powerful. If it was a Jumbo, there was something wrong with it or it had been de-tuned somehow. Even with the flywheel weight and the timing on full retard mine would still pull from tickover in 4th up a steep bank - more than a 340 Sherpa is capable of.

What do you mean by matched the cases? What sort of difference are you looking for? The Jumbo is the most powerful air-cooled trials bike I've ridden. Mine had the reed cage fitted, most didn't. With a flywheel weight and the ignition fully retarded it still pulled like a train and I could easily shut right off and bring the power back on in 4th gear up steep banks. With the timing at normal setting and no flywheel weight, it was very agressive Biggest frustration was the clutch action.

I see what you mean - maybe the filter In Motion supply is a replacement that does the job as I'm sure that the one I tried for my Armstrong is one that they sell for the Cagiva 350 - but my memory is lousy Maybe you could use a 340 Bultaco type filter as that is a round filter with integral hose, the filter sits inside the airbox and the hose is pushed through the hole onto the back of the carb, the hose has a groove that seals in the filter box opening to the carb Give In Motion a ring as they may know how to get around your problem. Not everything they stock is on the website. Also, one of the forum members owns a Merlin / Cagiva so expect them to chip in when they see this as they are bound to have an answer

That's good news that you may be able to rearrange, I was hoping to ride a few PJ1 rounds this year, so keeping my fingers crossed that any rearranged date doesn't clash with something else. As I said originally, it wasn't intended as criticism of anyone, there are so many events these days, events on the same date are difficult to avoid always - my club still gets date clashes with the local AMCA clubs occasionally, despite us all trying to do everything to avoid it. It was just sod's law I thought, that of the few traditional road based events that are left, we have three clashes... Just screaming out loud rather than criticising. As regards the support for the Miller rounds, the number of overall entries for each event is quite good but when you look at the class breakdown, there are sidecars and trail bikes in there as well as British and twinshock solos and it's the number of British 2-stroke and Unit classes that aren't as well supported as they used to be - in comparison say to the average PJ1 entry and of course Scotland or the Manx Classic. I take your point about the MSA requirements and this may well affect future road based events, although that is a different issue from the the number of Pre65 entries in the events over the last few years. I always thought that trials was automatic approval as if you look at the criteria for automatic approval, a trial seems to meet it fully. Interesting that the AMCA are continuing as they were because I agree with you, the amount of paperwork and hoops you have to jump through now is enough to deter anyone with a full time job and family commitments from wanting to get involved in organising a road trial.

I'm fairly sure In Motion have these as I'm also fairly sure I had one to try in an Armstrong. I think it is a filter with hose attached but that's not what you're describing from the parts book. Have you tried In Motion?

That wasn't a section...

Ross, it was only tongue in cheek But, I do think it's a shame that a series like the Miller doesn't always get the support it could get, given the amount of work that goes into organising them. It's as though there's a 'status' attached to riding Scotland that riders need in order to add a bit of gloss to their 'CV', whereas the Miller series barely gives it a dull sheen or doesn't have the same acclaim. Shame, as they are enjoyable trials and not overly demanding, which, from what I read on here, seems to be what most want from classic trials.

I know it must be difficult when fixing dates due to so many fixtures now and different organising bodies involved, but there are three date clashes for two of the main Pre65 road based series this year. The Miller championship and the Northern British Bike series. Both have events on 24th March, 14th July and 13th October. Both of the events on the 14th July are in Yorkshire so that is going to hit one series badly in terms of Pre65 entries. The Miller series is down to 7 rounds this year and for the life of me I can't understand why it isn't better supported by Pre65 entries, especially when you see the number of entries for Scotland. Two routes to choose from means a perfect balance of sections for standard to modified machines, but for some events the numbers are quite low. I can't believe cost is a factor when riders can pay huge sums for modified Pre65 bikes and many riders have more than one... These road events are slowly diminishing and need supporting to make it worthwhile for the hardworking organisers to stage them. Once they're gone, they'll never come back. Maybe Scotland should have a qualifying criteria - riders must have taken part in so many national events to gain entry, rather than riding just once a year...

That's the original stay from the alloy guards

Yes, two rimlocks didn't stop a section of it dropping off. I'm sure I've read on here or maybe seen at trials Yams with tubeless tyres being used, but I've never been able to get one to stay fully seated and that's on a TY twinshock and mono and a KT250. There is one way around it and that's the tubliss system. It works as I used it to fit a tubeless IRC to the KT but they are a bit of a fiddle when it comes to changing or turning the tyre - not as bad as fitting a mouse to an enduro bike though... Designed primarily for motox but works just as well in a trials bike http://www.tubliss.co.uk/. Not cheap but cheaper than converting a wheel to a tubeless rim

8psi is way too high for trials, so it's not giving an indication of whether the tyre will hold onto the bead at trials pressures which are between 3 and 5psi. At 8psi the tube is probably still fat enough to keep the sidewall out. On the Yam rims, after fitting and blowing out onto the rim, when letting down to the required pressure I found that once the pressure came down to about 9 - 10psi it dropped in. The Dunlops have the stiffest sidewalls but don't seem to grip too well with a tube in (in mud at least) I had a tubeless Dunlop on a tubeless rim on my 340 Bultaco which gripped fine. I then had a problem with the spokes leaking so had to fit a tube for a while and it was a different bike with less grip. No idea why that should be but it was. I think with the Yam rims, the safest bet with a tubeless tyre is to remove the edge of the bead to mirror a tube tyre as suggested by others who have done it

It's a tube type rim and normally the Yamaha rims won't successfully seat a tubeless tyre. It will pop out ok when fitted, but once the pressure is down to riding pressure they usually drop off the rim - at least all of those I've had did (twinshock or mono) Others may have found differently? The only tubed tyre is an IRC. The Michellin tubed tyre is as good as a racing slick in the mud, useless, it's nothing like the old X11 tubed tyre

Lesson learnt - get an old flywheel and chop the centre out. It must make life so easy! A potential problem there is that the cam may have worn differently on the flywheel you butcher so that the points gap is different when you put your own back on. Probably not enough to make any significant difference but with the luck I have it would be...

There was no cylinder head vent from the factory, it's somebody's modification

I've been told you shouldn't do this by an ex BSA man as it interferes with the way the pressurising / depressurising of the engine works. The explanation he gave of how the system works and the affect of adding vents made sense, but I can't remember it.... His BSA doesn't have any of the 'recommended' extra vents from Rupert Ratio or anyone else and it has no oil leaks

To stop mine from wet-sumping when parked up, I used to gently clamp (so as not to damage /crush the pipe) a pair of flat jawed mole grips onto the oil feed pipe from the tank to cut off the the oil feed. They'd stick out of the side of the bike so there was no way I could forget to remove them when starting the engine. This stopped the wet-sumping at least and therefore leaks when sitting in the garage. The leaks themselves could be anything from damaged gasket faces, wrong type sealant etc. If it spews out oil when running, a possible cause is pressure build up due to the venting system not working properly. Adding extra vents as is sometimes suggested doesn't cure this (I've been assured by a BSA specialist) so first thing to check is that it is venting properly from the vent in the bush on the crank (where the cam is) and through the airways in the casings on the clutch side.

I did, I suggested this about a week ago, along with eliminating the kill button as a possible cause (it probably isn't but for £12 - 15 I'd have replaced it anyway, or at the very least disconnected it. But focus went back onto the carb. If fuel is left on whilst the engine isn't running and the carb floods, it will pour fuel out of the overflow and it can also run down the inlet and fill the crankcase (and I mean fill it, you won't believe the mess when you eventually get the bike started and it burns off whatever is left after kicking with the spark plug out) If the carb floods whilst the engine is running it will still pour fuel out of the overflow but the engine will also run very poorly due to over fueling, probably 4-stroking at best, like running with the choke on when the engine is warm. None of these symptoms have been reported which is why I suggested eliminate the electrics first. When the bike is running it runs fine so it's very unlikely anything is wrong with float levels, timing, jetting, fuel/oil mixture, crank seals etc.

Truthfully, I have no idea. The ignition was fitted in Spain when I had some work done on the bike by Vasquez. I just had a fiddle with it to soften off the throttle response by retarding it a bit. I haven't a clue what it's set at.