trapezeartist

The Beta 4T is quiet. Not so sure about the Montesa. It’s also about the quality of the sound though. I think like-for-like a 2T has more potential to annoy non-petrolheads than a 4T.

Only 30 years? My trials hiatus was somewhat longer, and no road bikes, enduros or anything else in between. I started with a Beta 300 4T and it definitely got the better of me. I switched to a twin shock Fantic 200 and got on better. But after a year I’m going to switch back to a modern 200 or 250. The Fantic is a lovely bike and more knowledgeable people than me will say it’s the best twinshock bar none, but I think you have to have a passion for classic bikes to ride them, and I don’t have that. I will continue to enjoy riding with the classic clubs though.

That's a neat summary, Lineaway. Perhaps I need to go and start a Montesa v Beta thread. I definitely am not in the hop and bop contingent. One problem with the Montesa is that you have to go at least two years older for the same money. And the weight?

Indeed there are, section swept. And I'd be open to any, but the amount of information to be absorbed is pretty mind-blowing. Which year the significant changes came in? Which year there were problems. Which year it was a fiery beast and which year it was all soft and friendly. I started this thread because I think I'm getting on top of the Beta info but then saw an attractively priced advert for a Sherco, so I thought I'd ask.

I would be looking at a 2014-2016.

Right then, Sherco fans. Tell me why I should buy a Sherco 250 and not a Beta. Or not, as the case may be.

Remember, Yorkshiremen don't understand that there is anywhere except Yorkshire. No doubt it is a good centre for trials, but so is the Westcountry (in the widest sense of the word). Dartmoor and Exmoor provide brilliant trials territory. I live further north, but less than an hours drive gives me the option of the Mendips or the Cotswolds, or I could hop across the bridge (now free!) and sample the delights of Welsh Wales.

Not in any way that you would recognise today.

I was in at the beginning of National Type Approval, but we never got very far with Type Approval of the Delorean before the company turned up it's toes. All the work was development and self-cert for the US market. (And some interesting preliminary stuff on passive restraints.)

Interesting.

Good point about the engine running backwards, SectionSwept. My Fantic does that occasionally at the moment. The improved chuggability (is that even a word?) of the exhaust restrictor is attractive and I would guess it would also balance out any top-end boost that might come from the higher ports. Provided there isn't a heat issue (and you guys are reducing my concerns on that score) it sounds promising. I've just been doodling some calculations and it looks like a 1mm extra base gasket lowers the compression ratio from 9.0 to 8.0. That sounds about right. Easier starting would be a bonus too. Costs of the two compression ratio options are closer than expected. Assuming the head has to come off to change the base gasket, and the engine will end up with two base gaskets, that's going to cost about £70. A low compression head and head gasket will cost about £85. Whatever ends up being the solution, I fancy buying a 250 will be the way to go. Unless a good 200 lands in my lap.

Has anyone ever made sense of the quoted compression ratios in the official Beta specs? 125: 15.9 (totally unbelievable!) 250: 9.0 300: 10.9 200: different again, but I don't have the info to hand now

An extra base gasket is obviously similar to a low compression head. As well as affecting compression ratio, it will also increase the squish clearance which will also be good for softening power. It will raise the port heights too. I'm struggling to get my head around what that will do. The higher exhaust may reduce power as the last bit of pressure will be lost. Higher transfers might reduce low speed power and restore a bit of top end. Am I right? Richening it up is an interesting idea. As an ex-karter, I'm naturally disposed to running as lean as possible so I'm going to have to rethink this a bit. How did you do it? Main jet or needle position?

I've played with quick and slow throttles on another bike. When I was an even rawer novice than I am now, I thought the slow was good. But then I found that occasionally I wanted a good handful of throttle without needing to move my wrist too far. So I'm not a big fan, but it's a cheap mod and I would almost certainly give it a try. Washer in the head pipe, nhuskys? Do you mean the exhaust? I would be a bit concerned about the back pressure and the effect it might have on cylinder temperatures. And I would certainly expect it to affect carburation. I had thought about a restrictor in the inlet, but that's really no different to adding a throttle stop. And a throttle stop is not much different to a slow throttle where it becomes impractical to wind it all the way round. These are the reasons I was thinking about low compression or retarded ignition. They would hopefully tame the engine all the way through the rev range.

There's a general consensus around these parts that the Beta 200 is the ideal bike for novices and other riders of limited ability. The trouble is, in the secondhand market, 200s are as rare as virgins in Essex. So I got to wondering what it would take to tame a 250 down to 200 level. You can get low compression heads at modest cost. How much difference do they really make? What about retarding the ignition? For sure it would reduce peak power to a manageable level, but would it then hurt the responsiveness or the ability to trickle around on next-to-no revs? Is it even possible with the CDI ignition?

I take your point. I've worked in vehicle safety too (claim to fame: I've crashed more Deloreans than anyone else in the world) and the prospect of anything heavy flying about inside a crashing car is scary. However, we all have to pick our risks otherwise we would spend all our lives in bed and then worry about whether the ceiling will fall on us. We're motorcyclists: we can't be that risk-averse!

Blimey. Minivan? One of those Jap things used by florists?

You make a very good point. Any method of fixing your bike needs to have some redundancy ie failure of any one strap or component doesn't lead to catastrophic results. If I were carrying a bike on a trailer I would use at least three straps (probably four) so that failure of one strap wouldn't let the bike fall over/off. As I carry my bike inside a van-like car, I don't need extra straps. If the bike falls over, it can't go far, and it certainly can't end up sliding down the road.

Are you really sure your bike won't go in? I carry mine in a Citroen Berlingo car (with the rear seat removed and the passenger seat a little forward of normal). I've seen people carry a bike in a Renault Kangoo too. I can't imagine there are many vans smaller than that.

I share your concern but for slightly different reasons. The 70kg is a static limit that makes a sensible allowance for dynamic leadings. I once had a largish 2 axle trailer. The static nose load was quite modest but over bumps it yanked the back of the car all over the place. It never did any damage, but I got rid of it pretty quickly just in case. My concern is insurance. If your limit is 70kg and you put a 65kg bike on, plus fluids, plus rack, plus mud, you are exceeding the limit. If you have an accident you insurance company will be looking for any excuse to not pay out. And you just provided one! Even if it’s completely irrelevant to the circumstances of the accident.

Oni Nou has an "unconventional" sense of humour. I think he's amused by the thought of helmets being scrutineered at a trial, because it is so unlikely.

As I understand it (leaving myself a get-out there), hydrogen embrittlement can occur when chrome plating, but is not inevitable. Nonetheless, I would opt for nickel rather than chromium, just to be on the safe side. However, if you're buying a 30+ year-old bike and there are no cracks in the frame, I wouldn't be too worried.

Nothing to do with fwd. Mercedes just seem to have a liking for big castor angles. True of C Class, E Class, maybe others.

Again Im comparing Mercedes car with Mercedes van, which may or may not be relevant. My C Class has an extreme castor angle so it knocks out the shoulders of the front tyres.

I don't know if its the same engine, but i have a direct injection petrol in my Mercedes car (1.6, turbo, intercooled, about 150bhp). It's not the most refined engine in the world when revved, but it's very nice when driven smoothly and gives diesel-like fuel consumption.