Rev3 Engine Size?

[richierich]

Hi,

I think this is my first post on here despite being a member for a couple of years now; I am 50 something years old, in South Wales/Borders and ride easy/50:50 routes as a novice. Have been for 3 years now and loving it.

A friend has bought a 2007 Rev3 (road reg as 250) for his son as a first trials bike. The lad is 17 and an accompished H&H rider so not a novice by any stretch. The bike is mint and was the right money but having ridden it, there is no way it is a 250. Several other lads who are regular trials riders have also tried it and agree.

Lampkins ran the frame number through their records and say it is definitely a 250 so we can only conclude that it was recorded as a 250 in Italy before being sent out to the UK.

Without removing the barrel (cheapest way to see the piston - base gasket only), is there any other way to confirm the engine size?

The lad is riding Clubman/50:50 and is struggling with lack of power and I can see why. Before it is offered for sale, we would like to know the correct engine size so this problem is not sold on down the line. In all other respects, the bike is mint.Just not powerful enough.

Hoping someone can offer an easy solution.

Cheers

[bilks]

You could just take the cylinder head off,measure the bore size.then you would only need the 2 o rings.

125 bore size 54mm

200 bore size 64mm

250 bore size 72.5mm

270 bore size 76.0mm

[zerorev3rev4]

Remove front pipe lower piston and I can imagine you can get something in to reach opposite side of cylinder poss tape measure and measure to piston nearest to you .you should be able to get a good enough idea with measurements in previous post

[2stroke4stroke]

I was going to suggest pipe removal too - it just slips out the silencer. However, a 17 year old should not be "struggling with lack of power" from any Beta in 50/50 sections. I've seen hefty adults manage fine with a 125 (and they seem to be up to World round sections after all). I'd suggest there is something far wrong with the bike, not related to capacity. I have a 200 and it pulls high gears nicely. Perhaps try checking the timing or compression? Who knows maybe there's even a ring missing but you'll see when you remove the pipe.

If there's one thing forty-odd years of trials has shown me, it's never to be surprised at what you find wrong with even the best looking of bikes, no matter how unlikely or impossible it might seem. There's no better penny-pincher than a trials rider :-)

Edited April 7, 2015 by 2stroke4stroke

[richierich]

Thanks for the valuable suggestions and sizes, guys. Am going to try the exhaust port method using a depth guage on a vernier to measure the bore/piston diameter.

The bike is well up on compression, ticks over and runs without fault. It just does not pick up like a 250 (or 200 for that matter) off the throttle. If you can imagine a slow/black throttle multplied by 2x slower, thats kind of where its at.

I agree, a 125 will do the job nicely, but this particular bike is just unacceptably slow to respond and runs out of puff too soon on the steep sections. Even with a skinny 17 year old on board.

Will measure and post the findings but I fear I am with 2stroke4sroke on this and there may be more to it than that.

[bestrcpilot]

I would check the timing and the reeds. If the timing is way out it will not rev, broken woodruff key broken?

[2stroke4stroke]

A long, long time ago (topical, given today's auction?) I came across a bike that badly affected. The tube in the silencer had become dislodged and was blocking the exhaust - but you would hear that from the note. Worth checking the exhaust anyway?

[naichuff]

You could check out the exhuast for retriction in this would also kill the power

My 200 looses power then repack tail pipe and after a short run it is ok again

[mcman56]

It would be worthwhile to inspect the piston and exhaust. I once bought a Techno that ran as you describe. The power was sort of like a TLR200 but it would rev a higher. After checking everything, I pulled the cylinder and found the bottom of the skirt on the exhaust side was bent in. This must have disturbed the port timing. It looks like someone had the cylinder off, rotated the crank and crashed the skirt into the case. The bend was maybe 3/8" high and complete with a crack but was not loose or broken off. Cylinder compression felt good when kicking and there were no weird noises. A new piston was the cure.

[lineaway]

There are many things that could be the problem. Plugged mid-pipe, bad mains, stator, coil or just a worn top end. My older Beta`s always ran fine. But I had a 2003 like this that I never figured out, and last year a 2006 that had a very poor amount of power. Both were 250`s.

[huski]

Check the basics first .Ignition timing,clean air filter ,carb clean and check jetting,does the carb slide go all the way up,are the reeds ok?With older bikes that you dont know the history of never rule out anything.It shouldn't feel gutless whatever size it is and its most likely a 250 given what Lampkins said and the .compression it has .

[worldtrialchamp]

there is an obvious external casting difference between 125/200 and 250/270 cylinders. The header (exhaust) pipe on a 125 is also quite different to the 200/250/270. Should be easy enough to narrow it down just by looking at some close up photos of the engine or examine other bikes.

The engine/frame number series are also contained in the engine parts manual (attached). But this alone doesn't guarantee modifications haven't occurred.

http://www.trialscentral.com/forums/topic/55054-my-new-06-rev3/page-2

that topic has a close up of both sides of the engine and the exhaust. A 250/270 should look like that.

Edited April 8, 2015 by worldtrialchamp

[richierich]

Apologies for the delay; bike was dropped off with me this week and here is where I am:

 

Measured bore through exhaust port and it is a 250

 

Plenty of good compression and piston looks fresh through the exhaust port (where I would normally expect to see most wear).

 

Mikuni carb fitted with 145 main jet. Needle looks almost parallel..numbers are 5C23 and atomiser is 145RD.

 

A spacer was fitted between the reed block and the engine effectively drawing the reed block out by about 5mm. Apparently Beta say you can throw the spacer away if you want but I am suspicious it should have been fitted between the reed block and the rubber manifold??

 

All going back together without the spacer to see if there is any noticeable difference.

 

Any comments appreciated.

[tt3506spd]

I have heard of engines giving them sort of symptoms and turns out the piston was in backwards...

[steve_earle]

I have heard of engines giving them sort of symptoms and turns out the piston was in backwards...

I agree, that can give them symptoms.

 

With the piston in backwards the ring lands can melt as they are at the hot side and melt into the piston skirt if the bike has had a flogging.

 

Seen that before.