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Beta Rev 270 - how to make it slightly more "versatile"

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Hello! New member here, so please be patient¬†ūüėÖ

I've got a few months ago my first trial bike, a 2007 Beta Rev 270. After a few weeks I started having fun on it, but I kinda crashed against a few "limits" of the bike: speed and power.

Of course they're not made to be "fast", but I always have to front some km on the road to reach nice places to have fun... and the bike is too slow, to the point of being dangerous. My bike has a Mikuni carb that I'm dying to swap, as it always needs the air screw to be adjusted... and I always hated Mikuni, even when I had KTM supermotos.

Anyway, I'd need to make the bike a bit faster/more powerful to not be crushed by cars on the road. Since I want to swap the carb anyway for a PWK 28... would it make sense to get a 30mm instead? I guess I'd lose some throttle response down low but should get some power up top.

I already swapped the front sprocket to a Z12... but the bike is slow and there aren't bigger sprockets available on the market (or smaller rear sprocket, 41 is the smallest available).

As you can guess, I don't want to turn it into an MX bike, mind you... I have a lot of fun on the bike as is but for "commuting" between home and the nice places, the trip is awful and dangerous. 

I also tried to ride with more air in the tyres... didn't make much difference, but was worth a try! ūüėõ¬†

Before you ask: the bike is in good conditions, clean air filter, clean carb, good compression. Usually starts with the first kick. Thanks in advance!

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I think you'd be better off with a different type of bike.

For sustained speed you'll need to look at engine cooling, you can get an uprated pump and remove the radiator cover when on the road. Brakes are also likely to overheat and at least fade. Tyres won't last very long at all. Suspension damping is all wrong and geometry is iffy.

I used to ride on the road to a practice ground on an EVO and came across most of these problems when I tried to ride at normal road speeds. As it was on quiet roads I could avoid any problems by simply riding slower.

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Thanks for your reply... don't get me wrong, I like the bike as is but the commutes on the road are dangerous due to the low speed. I don't want a sportsbike, I already have one... would just like to have some more speed/top end to reach the nice spots where I can be a jackass at lot speed¬†ūüėĄ

I'd go for a smaller rear sprocket, but Z41 is the smallest available, and I already have a Z12 front (instead of the stock 11)... so gearing isn't the answer.

I never use full throttle for more than 1-2 seconds, mind you... that's why I'd need taller gearing, to keep relatively low rev but still manage to be fast enough to not be an obstacle for cars.

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The first week I had the Sherco, I drove it 8 miles across town to get to an event I wanted to check out, and the 8 miles back. It was exhausting and horrible. I kinda swore off ever doing it again.

 

It’s just not fun riding them on the road. 

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Yep... but unfortunately I have a few km around town to do, wherever I decide to go... so it's a necessary evil.

I just found out there aren't bigger front sprockets but Jitsie makes a Z38 rear sprocket... might be good, as mine is pretty worn.

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You will probably be able to get other sizes of sprocket that aren't listed for the bike, I can't see the bolt spacing being unique, try somewhere like tallon.

 

Before committing to gearing up though I'd suggest removing the radiator cover to aid cooling and then briefly screming it to get to 50mph+ on the road to experience just how bad the brakes and handling are, it might put you off.

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29 minutes ago, Triad said:

Yep... but unfortunately I have a few km around town to do, wherever I decide to go... so it's a necessary evil.

I just found out there aren't bigger front sprockets but Jitsie makes a Z38 rear sprocket... might be good, as mine is pretty worn.

I hope you've taken notice of what Totty79 said.
By the time you've geared it up that much it might also be very "interesting" for riding trials, especially with badly worn tyres from the road riding.

Even mores so if you swap to a 30mm carby!

It sounds as if you're almost trying to reinvent a light enduro bike to me.

Go for it if that's what you want to do, it could make the perfect bike for you. Just be well aware that every step away from it's standard form is probably going to make it less fun for trials.

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21 minutes ago, bikerpet said:

I hope you've taken notice of what Totty79 said.
By the time you've geared it up that much it might also be very "interesting" for riding trials, especially with badly worn tyres from the road riding.

Even mores so if you swap to a 30mm carby!

It sounds as if you're almost trying to reinvent a light enduro bike to me.

Go for it if that's what you want to do, it could make the perfect bike for you. Just be well aware that every step away from it's standard form is probably going to make it less fun for trials.

Light enduro, or 80’s/90’s mono… 

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27 minutes ago, Nishijin said:

Light enduro, or 80’s/90’s mono… 

Exactly my thought too!

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Nah, not trying to change it much... as I said, I'd just need it to be a bit faster for the commuting between the "zones".

I like pretty much everything else... the weight, the simplicity etc. - it's perfect once you're in town or in the woods. But getting there is the problem.

A bigger carb isn't going to make it a CR250 LOL, they went from the Mikuni VM26 to the Keihin PWK28 in 2008... I doubt a slightly bigger carb will make such a difference as the cylinder still has ultra-tiny in/out ducts (sorry, don't know the technical terms in English).

Of course if it has to lose the snappy throttle response, not worth it. But the Mikuni is absolutely unpredictable: yesterday night the bike was crispy and powerful, almost lost me when decided to wheelie in 5th gear uphill... maybe the carb settings like colder weather.

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Sounds like much depends on whether you want a trials bike - to use on trials type sections where you go to ride - or a bike which is OK just to blat about on some rough ground.

If the former, every alteration you might make to make it faster on the road will substantially detract from what you want it to do when you get to your venue while still leaving you with something that's basically a pain on the road.

If the latter, you really would be better with a lightweight trail bike which can still be chucked around but has a semblance of cruising/braking ability on the highway. 

Trials bikes are so specialised that they can't really be turned into something they aren't, high gearing or not. Trying to do so would be a costly route to disappointment, resulting in a bike which doesn't fill either role very well at all.

 

 

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I'm not (yet) good enough for "sections", I just try to learn something everyday... but yeah, what I'd like to do it "Trial" ala Julien Dupont... a trial bike is so much fun and I'm learning a lot. I doubt I could do the same with an MX bike... maybe, not sure. I'll try to ride one if I get the chance. In the meantime I guess you're right, I should probably just replace the rear sprocket to keep the revs low on road commutes and keep the rest as is... if it's not broken, don't fix it ūüėõ¬†

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The "broken" bit should come when you start on proper sections. All good fun!

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I think changing the carby to a bigger one will make a substantial difference to the low speed response - there is so little air flowing through at low revs already, and a bigger carby will slow the flow even more and become harder to get the low speed mixture and response right.

I think you're on the right path now - change as little as possible on the bike to get it to be barely acceptable on your commutes, then just ride it.

You used to be able to buy (or make) two speed rear sprockets - a normal smaller sprocket and a "ring" which slipped over that and located with a few bolts in the tooth gaps. You cable tied (or wired) the ring to the spokes when on the road, then when you went off-road you added a few links to the chain, slipped the ring over the main sprocket and away you went in "low range".

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Edited by bikerpet

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Like an MTB... but wouldn't be easy without the chance to keep the chain tension stable.

Anyway, I ended up replacing chain and rear sprocket with a DID520 and a Jitsie Z38... now I can keep the revs lower and keep a decent speed. Yeah, going to keep it as is for the rest, even if the Mikuni is still crappy... in the future, if I stick with it, I'll replace it with a PWK26 Polini, so same diameter but better in all aspects and won't flood the engine.

Gotta say, though, that the 2008 Rev has a 28mm carb and almost everybody says it's muuuch better than the 2007... so a slightly bigger carb isn't a bad thing. I highly doubt they modified the engine to make it work.

Edited by Triad

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