Making Rev 3 270 2T Easier To Kick Start

[bigbird2]

I JUST made a deal to get a one and now I am on a quest to make it easier to kick start. I'm OLD!!!

I had a thread on this on the General board - before I'd settled on a specific bike (and because I have a gal friend with the same issue) but thought you folks on this board might have more good ideas on this specific bike.

I'm thinking of retarding the timing - maybe 5 degrees???

I'm also thinking of adding base gasket(s) to raise the cyl - maybe 1mm to 3mm???

OR I was thinking of making a 2mm to 3mm replica of the head gasket out of aluminum as another way of increasing the combustion chamber volume without changing port timing???

Do you know anything about how difficult this would be to make?

Also would I want to used a standard head gasket on BOTH sides if it?

I guess I could also grind some metal out of the dome part of the cylinder head which would avoid messing up the squish area around the edges and not affect the port timing - but of course this is not reversible.

Although getting it to tuck in might be a problem - the idea of lengthening the kick starter seems like it would help too? Anyone know of a source for a broken on I could get to try it on?

Any thoughts you have will be appreciated.

Edited November 6, 2013 by bigbird2

[greychapel]

I had a 270 rev 3 was 55 at the time, never had a problem, (but I am quite tall) I found it best to ease it just over TDC let the kickstart up to 10 O'clockish then give it a steady firm push NOT a sharp kick....but if you are resorting to engine mods you have probably tried all this!

[dadof2]

Whatever you do a 300 has a large piston area and therefore will still need considerable force to overcome compression pressure, even if compression ration lowered. If you lower the compression ratio too much or increase the squish clearance too much you may have all sorts of engine damaging problems.

I would try a 1mm thick base gasket spacer. Any change greater than that and you will probably need to modify the head and or piston.

[tltel]

. If you lower the compression ratio too much or increase the squish clearance too much you may have all sorts of engine damaging problems.

Could you elaborate please.

TLTEL

[technowaldo]

Would it not have been a lot easier to have bought a 200

[bigbird2]

Yes but I was having trouble finding one this was a GREAT deal.

[nzralphy]

When i had a 270 I retarded the ignition timing about 3-4mm and it ran a loot smoother at lower revs.

I also removed the head and piston to polish (400/800/1200 emery then Autosol polish) the head & piston (both to a nice shine) then put in an iridium plug and it started and ran WAY better.

To lower the compression..... Some say putting in a base gasket moves the port timing up the rev range but you'll actually not feel much difference.

[mcman56]

I made a 1/16" thick head spacer for a 250 techno that my 4'10" 100 lb daughter was trying to start. It used o-rings instead of steel gaskets so was a bit different. It sealed with o-rings on one side and just RTV on the other. It ran OK and still does 8 or so years later but with fresh piston and rings was still too hard for her to start. With a mill and turntable, the spacer was not too hard to make. The Rev 3 steel gasket is also a water flow restriction so that would have to be considered.

The Rev 3 200 is a small bore 250/ 270 and not a big bore 125. It uses a bushing to reduce the small end rod diameter but all else...carb, exhaust is the same. I converted a 2008 200 to a 250 by installing the 250 top end. I have been planning to put the low hours 200 top end on ebay but have not gotten around to it. If you are interested send me a PM. I also think there is an older 200 cylinder on Uk ebay right now. The older ones used a steel sleeve but the 2008 is all aluminium. I don't know when Beta made that change.

Edited November 7, 2013 by mcman56

[bigbird2]

THANKS to both of you. I talked to Adrian at Lewisport and learned that he has successfully used as many as 3 of the 1 mm head spacers he had made for some earlier model Gas Gas 2t 250-300 bikes to tame them and make them start easier. 3 mm looks like it would lower the compression ratio on my 270 by about 1/3.

Edited November 7, 2013 by bigbird2

[0007]

Wow, compression reduction of 30% is huge if your calculation is correct

That will massively change the combustion pressure and temperature, big change in power, jetting and running condition

Basically it was not designed to run well with a major drop in compression like that so you are kind of making a prototype

I think I would opt for the 200cc top end if possible

[tltel]

Bigbird2, If you are thinking of lowering compression that much, I think you really have made the wrong choice of machine, If it was that much of a good deal, sell it on and get a bike that suites your needs better.

have you actually ridden this bike yet, you may be worrying about a problem that doesn't exist.

TLTEL

[graham _a]

This might sound odd, but how are you trying to kick the bike over?

The best way is to be right over the bike as if your balancing, so a bike stand under the skid pan is the ideal way for me initially.

That way I can let it warm up before i ride, and minimise clutch drag.

If your one foot on the floor like a conventional bike, the angles are all wrong with a Beta and it is a lot harder.

I'm used to mine now, and It gets easier.

I can pretty much start it first kick from most any angle.

[bigbird2]

Thanks Again for your input.

I don't even actually have the bike yet but have a friend with the same bike that I have kicked a few times.

I can start it but it is sort of marginal and I think it would get very annoying at best on a hot day when I'm tired, etc.

I don't need the power of the 270 so I'm thinking why not detune it and make it easy to kick (or go the 200 route)

Re: The 30% reduction in CR IS a lot but Adrian said it had worked well for several of his customers. I've found a 2008 250 manual that lists the CR at 11:4 to 1 - WOW --- I think the CRs on the early 70s trials bike were around 6:1

Edited November 7, 2013 by bigbird2

[mcman56]

Can you post a picture of what the head spacers look like before they are installed? I would be interested in seeing what a Rev 3 head spacer looks like.

The really low published CR may be from a Japanese bike. They tended to calculate an "effective" compression ratio. For this calculation, the stroke was from when the exhaust port was closed by the piston to TDC. This produces a smaller number but tries to give importance to port timing.

[nzralphy]

+1

There are two ways to get two stroke CR.

I think your maths is out somewhere and don't think CR will be lowered by 1/3