woody

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.

Some clever people in this world.... Who also know how to make a few quid... The unparalleled global viability of these new fuels lies not only in the exceptionally simple and relatively inexpensive process which creates them, but also in the fact that the ‘feedstock’ used to produce them is entirely renewable. Yet the cost will still be equal to the cost of a barrel of unleaded. Just when you think a cheap fuel alternative is on the way...

Virtually everywhere is now Pre70, not Pre65, so 4 speed not an issue. Definitely not in the Manx, Yorks Classic have their own rules on their website. Scotland is about the only trial that still runs to Pre65. 4 speed engines aren't a problem and are accepted in Scotland - up to now anyway. Just another vagary of the rules - probably because the first 4 speed engines look identical to the last 3 speed so unless you're checking engine numbers you can't tell.

The thing to remember is that these are trials bikes, not Motogp bikes and having the timing absolutely to the degree isn't really necessary. They'll run with the timing anywhere between 1mm to 4mm before TDC. Towards 1mm the engine pick up is slower, towards 4mm it's quicker, you just put it at the setting that gives the response you're happy with through experimenting. 4mm is a bit extreme I know, but I've run Ossa MARs at 3.5 in an attempt to liven them up. Works setting supposedly but it didn't make much difference. On my TYZ Yam and SWM Jumbo I used to run both with the timing fully retarded on the backplate which made the TYZ throttle response smoother and the Jumbo, which is an animal, less aggressive - neither is anywhere near the manufacturer's recommended setting. No problems with performance, both still pulled as they should and both would rev out cleanly. You'd need a ship's anchor to hold the Jumbo back anyway... I'd wager that if anyone rode my 340 Sherpa they couldn't tell me what the timing is set at from the way it peforms. If you want to set it to recommended setting, then surely the best way is a dial guage and multimeter with beeper, as mentioned before

I have read more about this phenomenon having never heard of it before. Perfectly normal if you've kicked hell out of a bike and it isn't firing. That puddle of fuel in the crank is only there because you have been continually drawing fuel in when trying to start it, some gets pushed out the exhaust, some stays in the engine. When the bike is running, that puddle of fuel will get burnt off, it doesn't stay there permanently, so isn't the immediate cause of the bike not restating after you have stopped it. This is where a decompressor is handy, if you kick the engine over repeatedly using the decompressor, it will help get rid of the fuel and help get it started. The only other way fuel can get into the crank is if the petrol is left on and the carb floods. Fuel will then overflow into the inlet and down into the cylinder. This will involve a lot more fuel in the engine than you describe. Why are you so reluctant to eliminate the kill button from the list of possible causes? Electrical problems defy all logic and sometimes you just have to employ trial and error. Disconnect it - at least it will prove whether it is at fault or not. I would also earth the coil direct to the frame and get rid of the wire to the engine - it's not how they are meant to be earthed, no bike left the factory like that. The point I was making earlier about a weak spark is that although the spark looks strong, that may not necessarily be the case and when under compression, the pressure inside the cylinder is enough to snuff out the spark. It has nothing to do with the kill switch knowing the plug is in the cylinder - it's simply that the spark isn't strong enough under compression to fire the mixture - despite it looking fine when you test it As I said, it's trial and error and you need to eliminate all possible electrical causes - including a nick in the wire from stator to HT coil, especially where it leaves the stator as they can always get pinched here when fitting the stator - just because it has been renewed at some time doesn't mean it's not at fault. Also, as someone else mentioned, cut a piece off the HT lead and refit the plug cap - even if the end of the HT lead looks in good order, just do it. The way you say your bike performs when it is running doesn't suggest anything wrong with carburation. Concentrate on the electrics until you have eliminated all that has been suggested.

Raising or lowering the needle in the slide will have no affect, it only controls the fuel / air mixture passing from carb to engine when the engine is running. If the bike isn't firing when you are trying to start it, the plug will be wet. It doesn't mean a flooded carburettor. If the carb was flooding the engine wouldn't run smoothly. You would also have fuel running out of the carb. A strong spark visually doesn't mean it can't be extinguished under compression if there is an electrical problem. You haven't yet eliminated the kill button, at least disconnect it and see if the symptoms persist, if you don't want to replace it. Are you sure there are no breaks in the wire from stator to coil Also earth the HT coil directly to the frame by rubbing the powder coating off the coil mounting bracket completely until you see shiny metal on the entire mounting face of the bracket. Earthing it to the engine may not be a good idea as the engine mounts are also powder coated and if these haven't been cleaned off thoroughly you will have a bad earth. Until you are certain of these things, you haven't yet eliminated the electrics entirely as a source of the problem

The way I read the exhaust rule is that you can have an aftermarket part like a WES etc. But you can't fit an original manufacture exhaust from a late model to an earlier model - so you couldn't fit a clubfoot rear silencer from a Sherpa M159 to a Sherpa M80 or M91/92 ? Same with airboxes. If you fit a 199b airbox to the earlier 199 or 199a models the bike is automatically moved up a class. Sometimes, things like this are done for practical reasons, not performance, as the B airbox is a more practical design and makes the filter easier to service. I've had a new airbox made for my Armstrong for the same reason. To remove the airfilter or airbox from an Armstrong Hiro is really awkward and time consuming. The one I've had made lifts straight out of the top of the frame, no need to remove the rear wheel and one shock absorber. No performance gain but this modification would put it into the Open class. Javier - what do the riders think about these new rules - from what I have seen of the bikes in Spain, most have been modified in some way or another which would put them in the Open class. I always thought the modifications to the bikes in Spain were sensible as generally the bikes still looked like the originals apart from all the bright paint, chrome and polish. The number of bikes using more modern components seemed very few - apart from the mudguard brackets and tubeless wheels. I don't undertand why there is a problem with tubeless rims / tyres = in any organisation.

Generally, they don't use them in Spain, there are one or two but in the main they use the originals - what the regs now prevent is using the late 90s Gas Gas style mudguard clamps and bridges, as seen on the Puma bikes. There are so many bikes fitted with these you have to wonder how many bikes will be in anything other than the Open class.