Modify Gori GP50

[Arfur]

Ok I currently have a Rapido 250 reed valve Gori gp50 exhaust. Not happy with top end tops out at 60. Was thinking of going RB25, can the Gori be modified to fit the RB?
I know there are plenty of exhausts for the RB but I like the box pipe setup.

[Warkton Tornado No.1]

If you can cut & weld, almost anything can be made to fit.

Will an RB be any better? Not if it's not set up properly, like the Rapido you have which must be set up badly to be so gutless.

A home made clubman (smaller bore 'U' pipe, 25 mm bleed to silencer, long reverse cone, side cut for ground clearance) is probably comparable with a Gori.

With that & a proper two stroke carb running through an adequate filter, no reed, a Rapido 71 x 61 comfortably pulls Pacemaker x19 x 46 (TV 200 top) & matches a tuned TS 66 x 60 with 34 VHSB & an expansion chamber.

I'd check what's wrong with what you have before changing course......

[Minority]

I know it’s not the question you asked, but I think you need to sort out that Rapido, something is very wrong . My home tune Rapido 230 reed valve is good for 85mph + (admittedly it has a TSR Evo expansion exhaust). If it’s the Gori holding the Rapido back, it might do the same for the RB!

[tony172]

Agree with above

[Arfur]

Thanks guys really struggling with it it heat seized two pistons on a BGM clubman so changed to Gori but can’t seem to get any power. 30mm dell lth Reed AF clutch and 5 speed box. Just can’t seem to get power screaming revs thought clutch was dragging but not that.

[Warkton Tornado No.1]

As a scooterists since 1973, my generation had very few 'clubman' exhausts available (Royspeed & Ancillotti predominantly) so made our own. One thing we learnt the hard way was about heat build up from the exhaust bleed......

I have had occasion to work on other people's Lambrettas fitted with the MB exhaust. IMHO the tailpipe is too small for even a 200, let alone anything tuned & bigger in capacity! Having a small tailpipe is all very well if you wish to manufacture an exhaust that ensures noise limitation & higher torque, but is unlikely to enable an engine such as yours to meet it's true potential.

If the Gori is anything similar, then I would consider trying an alternative of any kind if you can borrow something. Or try increasing the tailpipe size to @ least an inch bore.

[Arfur]

As a scooterists since 1973, my generation had very few 'clubman' exhausts available (Royspeed & Ancillotti predominantly) so made our own. One thing we learnt the hard way was about heat build up from the exhaust bleed......

I have had occasion to work on other people's Lambrettas fitted with the MB exhaust. IMHO the tailpipe is too small for even a 200, let alone anything tuned & bigger in capacity! Having a small tailpipe is all very well if you wish to manufacture an exhaust that ensures noise limitation & higher torque, but is unlikely to enable an engine such as yours to meet it's true potential.

If the Gori is anything similar, then I would consider trying an alternative of any kind if you can borrow something. Or try increasing the tailpipe size to @ least an inch bore.

Thanks Buddy the Gori is a significantly bigger Down pipe than the BGM no overheating issues now just a lack of power. I think it needs stripped and checked

[Warkton Tornado No.1]

If you've had seizures then something was wrong. If you've not fixed it, then obviously you can expect further trouble.

So far, the current set-up (apart from exhaust) has seized twice. If it's not due to the exhaust backing up, air leaks, carburation or ignition, then it really is due a strip down.

That way the crankshaft can be checked, reeds, petroil inadequacy, evidence of "four corner pinch points' etc.

Good Luck with it. Something to do when it's dreek about.

[Minority]

Just a thought, you said it was A Rapido 250 reed valve, so obviously modified to take a reed valve. Was a boost/finger port cut and the piston modified for 360 degree inlet timing? If not that would definitely explain the missing power, if not the seizing .