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But there is so little room to fit a bigger liner before you hit the studs. The Seeley/RS200/TLR200 bore is 66mm which, with the 57.8mm stroke gives 198cc, so there is never going to be enough room to get 250cc on bore alone as it would need a 74mm bore which means an OD on the liner of at least 78mm assuming 2mm thick liner. That takes you straight into the studs I think so they would need to be relocated along with the oil feed.
Maybe they stroke the crank too. Can't remember what the bore and stroke is on the TLR250 - 70mm bore I think which would make the stroke 65mm.
I don't know what you can stroke the crank to on the 200 engine - TL250 also has a 57.8 stroke and they were lengthened to 71mm in the works 305 long stroke bikes, retaining the 74mm bore, but I thnk on the 200 engine the gearbox gets in the way of stroking too far. Maybe they will go to around 65mm though but there aren't any 70mm pistons as far as I know as it is a bit of an oddball size.
Interesting stuff - shame I haven't a clue what the answers are, or the engineering skills to 'have a play'.
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That would explain why I've never thought of them as a proper trials bike. Didn't realise they did two models.
I'd love to see inside one of those 250 converted motors to see exactly how they accomodate the bigger bore, and to see what they do to the head/valves - then if I can just get someone to cast me a cylinder.....
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Nice job, just out of interest what is in it? Empty, a baffle, or core with packing?
Any idea what is in the middle box?
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The Seeley and RS200 share the same engine - the Seeley unit is plated RS200TE.
There are/were 220cc and 230cc conversions available in Japan for these engines, don't know who by but may well be Kondo. They use the existing cylinder so the engine looks the same externally. The 220cc is an overbore but the 230cc involves crank re-stroke I think, I'm not 100% certain of this. One thing is for sure though, there is very limited room in the cylinder to bore it out much, even with a new, larger liner, before you meet the stud holes. I've looked at my own engine and as RS says, it must take some extensive work to get them bigger than 230cc as the cylinder stud holes would have to be relocated by the look of it
As far as an RS200 goes, from what I've seen of them I'm not sure how competitive they would be. The steering looks very lazy and I've no idea what the chassis is like. Then there is getting one and the cost of it. They are as rare as rocking horse teeth here because they were never imported. Value seems to be above TLR200 from the few I've seen for sale. The ones I've seen also look like a trail bike (picture attached hopefully) although there seem to be several aftermarket tank units available.
What about a TLR 200. It would cost less to buy for a good one, the same conversion can be done to the engine, whilst it probably has a better chassis than the RS200 - unless you want something different of course.
You could always speak to Ian at Ellastone Offroad (number in TMX) as they occassionally bring in some of these converted 220 and 230cc engines (local bloke has bought one to put in his TLR200 although hasn't fitted it yet) I think they are around
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I fitted a remote hot start kit to my YZ426 a few years ago. All this involved was unscrewing the standard one from the carb, replacing that with an adaptor to which was fixed a piece of clear pipe (same size as carb overflow pipe roughly). The pipe went to a device on the handlebar which was just an on/off valve - when open it let air in to help with hot starting. It wasn't any more effective than the standard device in terms of starting efficiency but it just meant I didn't have to grovel with the carb mounted lever when I'd crashed and burned a stinking hot engine so it was a time saver.
The inlet into the carb (inlet side of the body) was I'd guess about the same diameter as the internal diameter of the pipe but all this is approximate you understand. I don't know how you would modify your carb to take something like this though.
In operation, as soon as the engine fires you knock the hot start off as it only serves to aid starting, the engine won't perform with it open.
I have a WR426 now with the standard hot start as I fitted a YZ450 cam which has auto decomp fitted and starting is much easier. If I can get the hot start button out I'll try and measure the intake hole for you but it may be a couple of days before I can do it.
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They were probably the best twinshock at the time they were current in terms of an all round package although people will always have their own opinions as to what is best as it can come down to personal preference. I certainly have no allegiance or affinity to Fantics as I had a nearly new 240 at the time and hated it. Couldn't get it to grip always and the power delivery was too snappy. I didn't give it much of a chance though and improving the way it was set up may have helped but I never felt comfortable and just wanted rid of it. It was used however and may have been messed with and it was also one of the first, later bikes were softened off but I never tried one.
There were bikes around that were more powerful and the Hondas had better suspension but the 240 just seemd to do everything well - even grip, maybe it was just mine. Clutch and brakes work well and the suspension and steering geometry is good. Basically, if it is a good one you just ride it and don't have to mess with anything. If you're tall though you can be a bit hunched over the bars and dropping the footrests would help that. If you're not it's not a problem.
I think the spares situation is reasonable so they are a viable proposition for regular use in twinshocks. Best thing to do is try one, but make sure it is a good one or you will not get a true impression of how they perform.
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I always wondered why the green. His current bike just has a green top yoke. Alex was at our centre trial at Hawkstone recently so I was able to ask. Green was the racing colour of Alex' dad's brother Simon, world long track champion.
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Had one years ago. Great engine. loads of torque and they find grip really well. Just the steering that isn't to everyone's taste as they have a fair bit of trail, similar to some Bultacos. OK until sections start getting a bit tight, then they can feel a bit long but not many sections like that in the twinshocks really. Some get on with it some don't, it can be altered if you know how/someone to do it, depends how serious you are.
I'd say they are only a fraction behind the best twinshocks which are Fantics and sorted Hondas/Majesties and on a par with the other later bikes.
Get it out and have a go.
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Guessed what he was doing as soon as you mentioned the mono engine as I was going to do it myself.
I'm not against modifications if they are 'period' but it is hard to define that. If it was something that could be done at the time, then it is ok. There was a lot more modification going on with bikes back then than people probably remember. Lots of experimentation with swingarm length and positioning, damper positioning, steering angles, exhausts, reed valves etc. but I guess the Yam Mono killed it all at a stroke. The bikes ridden by the works riders were always different from customer bikes in one way or another.
I was going to put a mono engine in a mini majesty or 175 frame to make a sort of replica of the last 'works' Majesty. These were smaller frames than the usual Majesty and had a special 6 speed motor, nothing like the twinshock TY250 motor, but very similar to the Mono. There were only about 3 or 4 of these bikes made I think. They were almost a mono without the mono, if you understand what I mean - pretty good. They were never offered for sale, works bikes only. So putting the mono in the smaller frame I thought was viable as it was sort of replicating one of those works bikes. Anyway, didn't have the skills to do it so forgot about it - and I probably would have felt like it was cheating.
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I don't think it will. The TY175 and TY250 twinshock have different backplates according to my mate who borrowed a 250 stator from me. I don't know this for sure myself as I don't have a 175 but he said the 250 plate wouldn't fit. Think the 250 may be larger diameter. The flywheels are definitely different.
So as the 250 twinshock and the 250 mono backplates are the same, I don't know what you would have to do to get the mono to fit the 175, if there is anything. On the 250 twinshock the mono stator fitted staight on and worked with the twinshock flywheel. It was just trial and error to find a firing point as the timing marks obviously don't align. Once it's fired up it can be timed with a strobe, or just trial and error until it runs ok. I haven't used the bike with this set up yet though but I knowof someone else who has/does and it works fine.
There is an electronic system (of sorts - I'm not too technically minded when it comes to electrics) available by Australian company called Atom ignition that is supposed to do away with points and work with any 2 stroke engine. Don't know where you get it from or how well they work but they are a heck of a lot cheaper than anything else available. Someone on another forum was trying one on a Sherpa but never gave any feedback as to how good/bad it was. I know you can buy them for Bantams for about
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I think the trail and twinshocks competed in the same class last year in the Sammy Miller series. Twinshocks were supposed to have their own class but it didn't happen untill this year. And they were also supposed to be Pre-76 and Spanish....
I can guess what is going on with a Mono engine. I was looking at putting one in a mini majesty or TY175 frame a while back along with other mods but in the end thought sod it as it was a lot of work, most of which I coulcn't do and ultimately, I felt it was cheating a bit so scrapped the idea. Then I thought, well, it's nothing that couldn't be done when twinshocks were still being ridden as the Yam Mono was a couple of years ahead of other monos, so I thought it could be classed as a 'period' mod. Then I thought sod it again, sold the engine and kept the ignition for the Majesty.
So, at a guess I'd say that a tweaked mono engine is going in a mini majesty frame with discs etc. Near the mark or way of..?
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http://www.allensperformance.co.uk/
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I never geared it back to standard for SSDT so back sprocket was (is) 43 teeth. I was up to 100kph on the road at times but that was in no way buzzing the motor - never felt under geared felt like there was plenty left but I never went over that. Likewise on the moors and tracks it would pull 4th and 5th so wasn't really buzzing it. Thought it may be because I had the vent holes taped over in the mudguard to stop muck getting around the airbox - maybe that caused it to run a bit rich.
I know what you mean about the brace and it could be why it took longer to refuel. It was really p*ssing the army guys off
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That very rarely happens though as he normally wins the t/s class in those trials every time. Have to disagree about the advantage the bike has - engine in standard form is far better than most twinshocks, as is the clutch, steers better, front suspension and brakes are better and the bike is lighter than all but the smaller bikes.
Fitting a hydraulic clutch won't upset anyone - again, nothing in the rules about it and personally I can't see anything wrong with it. After all, it's not as though your hiding a Honda or Yam clutch in a Pre65
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If you get to Cumbria this weekend you've gone too far! Dabster has urged me to try one of these Classic rounds (then the git hasn't entered himself) so I'll see you there.
Opps, might be a good idea to find out where it is - haven't even looked yet. Got the riding list through today, think I may be at the wrong end, could be a tad slippery at the front.
Think you should enjoy it Perce, couldn't ride it myself last year but it was reckoned by all to be a good trial, for the modern bikes too.
Dabster's not willing to move away from that Southern softie mud
Twinshock - you polish that bike any more, the frame tubes will be that thin they'll snap
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What a cracking picture. Certainly have been some nice ones in different topics recently. but the older ones are better...
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About the only rule for twinshocks at the moment is that the bike must have been manufatured with twinshocks as standard equipment. So for the ACU Classic series or the Sammy Miller series you would not be allowed to ride a modified monoshock, otherwise where would you draw the line - 300 Raga replicas with twinshocks
In club trials you can ride what you like probably as it is up to individual clubs. There is a TY Mono fitted with twinshocks being ridden regularly in the twinshock class around Wilts. area such as Bath Classic, Golden Valley. That bike has a huge advantage over proper twinshocks and wouldn't be allowed in the ACU Classic.
Personally, I don't see the point, don't think it is in the spirit of what riding a twinshock is about and is basically cheating. I like riding certain twinshocks because they were the bikes that were current when I started riding in the 70s and most were just a pipe dream as they were new and I couldn't afford one. They are the bikes I have a certain affinity for and would like to own now and ride whenever possible. Most of the later twinshocks don't really interest me as much so don't have such a desire to own one. There are the odd exceptions though...
As regards discs, there are no rules and a few bikes that run in the ACU Classic are fitted with modern forks and a disc. Personally I wish they'd ban them (discs - not the riders who have fitted them...) as it could be the first step towards more modifications and if that leads to what has happened in Pre65 it only adds to the cost of competing if you are to stay competitive and on an even playing ground.
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My 4RT seems thirsty on fuel. In the SSDT, I actually ran out on the Thursday run from Fort William to Chairlift, about a mile or 2 before the fuel check, and again on Friday on the moors but luckily only about 200 yards from the check. Don't know of anyone else running out, just me I think. It also seemed at the fuel checks that it was taking longer to top up my tank than the 2 strokes - which is strange given that it is a smaller tank - or so I believe as I haven't measured it.
Out of interest, I was told that according to Sandifords, the 4RT has a 2.2 litre tank and a range of 70-odd kilometres, whereas the 315 has a 2.7 litre tank but a range of 37 kilometres. This is what someone told me, I didn't get that direct from Sandifords themselves so don't know if it is correct or not. Didn't seem that way when I had run out......
Does seem strange that it uses more fuel than I thought it would. My old YZ426 Yam would do 2 hours plus racing to a standard motocross tank which was easily better than a 250 2-stroke on a similar sized tank. Would have thought that the 4RT and 4T would have shown the same fuel trend in economy.
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Cheers Johhny, definite possibility, had blood tests last week so waiting for the outcome and Thyroid is one of the checks, along with a few others. Of course, my body could just be crying enough now.....
One thing is for sure though, I am definitely hauling myself up to Cumbria for the next round of the ACU Classic on Sunday. I dragged myself around the SSDT so will do the same there as venues like that are not to be missed - especially after missing Bootle round due to the van tyre blowing out on the M6 on the way.
Looks like the Majesty is going to have to come out a bit earlier than intended for a shakedown as the Ossa is dead again (all of 'em...)
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Sounds like a cracking trial yesterday. I'd loved to have ridden and am disappointed not to have but some mystery thing has been leaving me drained of energy for the last couple of months and as I've had to retire from the last 2 events because of it I had to concede it wasn't worth going, and I really hate doing that. Used to ride loads of Llanfyllin trials in the 80s and they were always good events.
As regards routes for the twinshocks it's difficult to make a ruling as to which they should ride. How they cope with the sections depends on the type of bike and who is riding them. If you have competent riders on modern, well sorted bikes such Fantics, Hondas etc. then they are going to be able to and want to ride harder sections than an average Joe on an unmodified 70s twinshock. Same with the Pre65. A 'modern', modified bike with decent rider will want more of a challenge than the more standard bikes. I think it is easier to include a class on both Yellow and White and let the rider decide for themselves. That way they are all happy and no gripes about too hard or too easy. Having ridden the ACU Classic for the last umpteen years I have seen how difficult it is to cater for the wide range of rider abilities and machine capabilities on one route. That series desperately needs two routes to encourage more twinshocks and Pre65s back into it
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Yes, sounds like the Ossa is Steve Sell (think that is the right name)
He has made the fork yokes himself, put a reed block on the barrell and machined alternate fins out of the barrell to make it look like one of the last 4 fin motocross barrells. All very nicely done. If I remember rightly, I think he made a different swingarm for it too. There was a picture of him riding it in TMX in one of the trials reports a few weeks ago and it had what looked like Bultaco fork legs in it - absolute sacrilege......
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If you search the Scorpa forum you'll find the answer as it has been covered before but I think the answer was a definite no
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That could also be the bike that Derek persuaded Honda to loan to John Shirt. Don't remember Lejeune riding standard colour bike in 1987, only Rothman's but could easily be wrong on that.
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This site has catologue pictures of virtually all trials marques. Just look up the Yams
http://www.ataq.qc.ca/galerie/index.php
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