Engine Swap

[2005marke]

hello, I'm returniung to trials after retiring 20 years ago at the age of 18 !!. Having spent 20 years racing modern motorcross and enduros its time to return to trials. However the decision has been made to ride twinshocks as these were the bikes I remember, and I have recently switched to classic scrambling and just love the atmosphere that seems to revolve around the older bike fraternity.

Having obtained a couple of Montesa 242's one has done next to nothing so will be kept for best, the other has done more work but still tidy. The opinion on these bikes by others seems to be that they are a bit fragile and spares are very hard to find. Having rode them a few times they seem to be nice bikes to ride, but as I plan to ride them most weekends in club trials as well as twinshock events I am worried about keeping them going.

In the event of a major engine fault can I fit ty250 mono engine that I already have in the shed into the montesa frame and still be eligable for twinshock trials events. As far as I recall these were available at the time as twinshock montesas were still available new after the ty250 monos were launched.

The aim of this mod is not to improve performance, its just to keep the bike competing.

Will this be permitted?

[348mate]

Forget it mate, montesa parts are available if you want them bad enough.....242's a good bike dont waste it with a bloody yam motor!!

cheers S_M.

[2005marke]

Forget it mate, montesa parts are available if you want them bad enough.....242's a good bike dont waste it with a bloody yam motor!!

cheers S_M.

I have stripped them both down and replaced bearings and seals because they have both been unused for many years, however attempts to find any source of pistons or even rings was unsucessfull. Fitted new mikuni carbs as I am not a fan of the mk2 amals and they run realy nice no rattles etc. My main corncern is the gearbox as one of them shows signs of wear.

I have tried the usual suppliers, sandifords, mainly spanish, Bultaco uk, none could offer a piston or rings for the 242 so no chance of gearbox bits, it seems that 248 and 247 cotas are a bit easier to find parts for. Should I be looking abroad if so any contacts would be appreciated.

[vintagecota]

Try these blokes...

http://www.rectificados-bellavista.com/PRODUCTOS.html

[stu]

The only real problem with the 242 MONT is the gearbox, bearing in mind that the basic bottom end motor is the 123 it can be fragile (same for the bigger 330) shafts tend to twist, very slightly making gear changes difficult, 1st is very low and lends itself to this problem when changing down, take care and you've got a really good twinshock and last of the real Montesa's.................

[2005marke]

thanks for the replies, and I will try and keep both montesa's running, but to get back to my origional question. Will I be able to run a yamaha engine in the montesa chassis in twinshock trials ? I know it won't be a problem in my local club trials as I am normally the only entry on a twinshock anyway, but will it be allowed in the classic trials ?

[mattylad]

I am going to fit a twinshock engined from a TY250 into a Montesa frame.

I think this is more "in the spirit" than a mono engine.

(Reason- I have both lying around).

The real question of course is when will it end.

I also have a TLM 260 engine as well!

[2005marke]

thats is the same reason that I am considering having to do the same, in the event of a gearbox failure it seems easier to use the TY250 engine that I have already than finding another gearbox. But is it pemitted in the bigger twinshock trials ?

[woody]

To answer the specific question 'is it permitted' is difficult as there probably isn't a specific rule that covers it. The only ACU ruling on twinshocks is that in the ACU Classic championship the bike must have been a twinshock at original manufacture and cannot be fitted with discs. In club events it is really down to the individual clubs what they will allow. Some allow Yam monos with twinshocks fitted to compete in and win the twinshock class, so fitting your 242 with the mono engine shouldn't upset them.

In the ACU Classic the rules restricting modification are to stop that sort of thing (because where do you draw the line, a GasGas or 4RT with twinshocks should just as readily be accepted iof a Yam mono was allowed) and really to try and keep modification of the bikes ridden in the series to a minimum. A standard twinshock is more than capable of tackling the sections which are nowhere near as tough as the centre/national trials of the era, so there is really no need for serious mods. Bikes are more likely to be personalised than modernised.

Given that some 240 Fantics are fitted with engines from the later 303/305/307 series then by definition, fitting the Yam mono engine in the 242 is no different. No-one bothers about the Fantics being updated with those motors so the same should apply to the Mont. But, it's also a problem of perception. The later Fantic engines look the same as the earlier ones, so it isn't an obvious update, unless you know what you're looking at, so the bike still looks standard. The Yam engine in the 242 will be an obvious mod. Does it matter? The Yam motor is superior in terms of performance so it could be argued that you're going to get an unfair advantage. My view is that yes, the engine is better but the events aren't about the need for power so it isn't going to help you float up the rocky streams of Bootle etc. It's also a mod you could have done when the bike was new as Yam monos were out 2 years before the others so they competed against (and slaughtered before finally killing off....) twinshocks. I'd say it's ok, don't know what other reactions would be - of course if you win on it, that will change peoples views, if you're at the back of the results, no-one would bother. People, as well as rules, are never consistent....

The only problem with mods like this is that it starts to push boundaries and you get the 'well if he's done that, I'm doing this situation'. And then where do you draw a line before it gets too far.

[peterb]

Well articulated Woody, I do like your answer.

Fortunately, we are not so governed by rules here in NZ probably as there are few enough riders not to be overly bothered about changing specific age related motors/frames/parts around. It's more so about the spirit of competing in trials, somewhere along those lines!

Bye, PeterB.