Mileage/Reliability for an iron barrelled 225

[mainstand]

Is it a fair bet that it's not ideal to rally 100's of miles on this set up?

I cannot for the life of me source 67.5mm thin rings anywhere so I'm guessing the only option left if I keep this barrel is to go up to 225.

Anyone recommend this way forward or be set against it?

[jonashford]

Nothing wrong with steel barrel for loads of miles

[mainstand]

Yeah I know that mate, as I have done thousands on this barrell, I'm talking about the 225 scenario

[Eden]

Ive done many thousands of miles on my cast 240. 71mm bore.

going to 70mm is no problem at all. The GT kit ive been ridding this year is 70.5mm bore.

[mainstand]

Ive done many thousands of miles on my cast 240. 71mm bore.

going to 70mm is no problem at all. The GT kit ive been ridding this year is 70.5mm bore.

I saw your scoot at Warsop & was going to find you for a chat about this but I had to slope off as the old bill came on site looking for me.

[CHRIS in MARGATE]

I am at 70.8 and have done nearly 7000 miles. Put a new piston in 2500 miles ago due to circlip escaping. To be honest I do run a tad richer than normal and I am forever blipping it to keep fuel going through to cool BUT that bored out and heavily ported iron barrel doesn't stop me from having the "grin factor".
I have revved it to 8650 and it would go some more but I I also ease up a bit at times and back of the throttle to where its richer and 4 strokes a little. Very reassuring sound.
Just back week before from 250 mile round trip rally and I was first through the gates in our little possee, putting my tent up.
Secret is...don't run weak and overheat.

[Eden]

Yup. Good advice there

[mainstand]

Eden, didn't I read you have had seizure issues?

[jonashford]

I have a steel lined rb barrel, 72.25 I think the bore is. Runs fine over long distances, keeps cool & hasnt seized once this bore round

[Eden]

Eden, didn't I read you have had seizure issues?

tends to happen if you ride flat out for long enough lol but with cast iron its no big deal

[Dimitrios_231]

Hi Eden,was it a Kawasaki conversion?
I'm always thinking of doing one.

[Eden]

my 240 is yes.

blog about its development is here, warts and all

http://www.lambretta-images.com/archive ... tta-p1.php

[Dimitrios_231]

Fantastic,thanks.

[MickYork]

Fitting one of the large Avanti heads may help with the cooling. They seem to be getting used on Rapido's and TS1's a fair bit with good reports.

[Adam_Winstone]

70mm (225) is no more or less reliable than 66mm (200) as the walls are still plenty thick enough not to give issue. Much of the unreliable reputation is because many people going out to 225 also start altering porting, compression, carbs, pipes, etc, all of which can make a 200 equally unreliable.

I've done thousands of reliable miles on 70mm bores, running them at constant higher touring speeds and putting enough miles on them to need further rebores beyond 70mm. 70.8 is the biggest that I've run myself but I have rebore oversizes going up to 71+mm.

Obviously, the head needs to go up to the correct diameter too (71mm for a 70mm bore, unless do welled for alignment) and the combustion chamber should be increased in volume so that compression remains suitably low for regular reliable use.

Good luck and enjoy

Adam

[jonashford]

I've used an avanti head on my rb for over a year now very good piece of kit

[Dimitrios_231]

This is a standard bore,untuned Autisa 200cc cylinder that I have and feels like the perfect base for a long stroke (62mm) Kawasaki conversion.

[Eden]

whats the measurement from the top of the barrel to the top of the transfer ports?

[Dimitrios_231]

47.83mm

[Eden]

perfect for a 62