Best pre 75 Four stroke motor ?

[firko]

That 250 of your sounded like a hairy goat Rossco plus good 4T engines are in the same league santa claus and the tooth fairy. I've seen a 250 Maico and they would be a doddle to get some serious torque out of.

Sure, Maico 250's can be made to work. Gary Treadwell did mine and did a very fast one for Cary L'estrange in Condoblin a few years ago but they become a bit unreliable (unless you use a Yamaha rod and big end kit). The biggest thing to overcome with a ported 250 Maico is the 4 speed box. If ever an engine needed a 5 speed it's the Maico 250.

good 4T engines are in the same league santa claus

Did you get run over a 4 stroke when you were a kiddie Lozza? Have you ever considered that some of us might like 4 strokes?

[Lozza]

I never even crossed my mind . I've never owned (and likely never will) own a 4T motorcycle. I see they sell them so somebody must like them, but I see they sell Andre Reiu CD's to.Each to their own I suppose.
Making your 250 Maico go Rossco that's a doddle.The engine has to work with the gearbox for sure. It might only need 1 ratio changed 

[firko]

It might only need 1 ratio changed 

Which would be? It's a bit of a problem when all Maico 4 speeds are the same ratios. As for gearing, you can always get a compromise but you'll never get the ideal. You don't see too many 250 Maicos blitzing the field for that reason. It's not a problem for the 400/440 because of the great torque available.

[Rosco400]

Have tried a few gearing combinations Lozza and try as you might, the 4T get the power to the ground much better than the 2T.

In the Pre 78s 263 and over, I had the 77 AW honking but could only manage a 5th in the final as the 4T made the 2T look stupid off the start line and they were some of my better starts on the day. Unfortunately, you cant win races from the back of the pack on the start grid.

Ray Stevens power to the ground on the 500 was amazing to watch when you sitting behind him (not thru choice I might add ) but it was what it was. I spoke to one of the other guys in the same class who has a long racing history and is no slouch and he had formed the same opinion and couldnt get his 2T to the front either, I cant remember the results overall but I would believe 4T finished 1,2 & 3 in the pre 78s.

Now saying this, i believe the 2T are still the go on th MX side of things and In not about to change the whole Maico stable over this issue, just would like a DT bike that is able to get the power to the ground smoothly and consistantly, sure its all got to do with the firing of the engne but I'm just not that technically advanced,I just like riding and observing

It might only need 1 ratio changed 

Which would be? It's a bit of a problem when all Maico 4 speeds are the same ratios. As for gearing, you can always get a compromise but you'll never get the ideal. You don't see too many 250 Maicos blitzing the field for that reason. It's not a problem for the 400/440 because of the great torque available.

I do have to say the 2T did finish 3rd in the pre 70 open against the big bores and was quick thru the dog leg because of the gearaing and weight issues, (no not mine) I reckon my old square barrell has more tow than the 400. Saying that , Keith Stacker had done a little head work with it 

[Lozza]

Could well be Rossco, the 4T will fire once every 720deg of crank rotation and the 2T once every 360deg of crank rotation. The idea is still used today on MotoGP engines. Theory on why is due to the 'gap' in the torque pulses allowing the tyre time to recover and find grip before the next torque pulse comes.Well that's what Warren Willing said and I'll run with that.
With a Maico 250 putting 27 HP or so at the wheel it's probably 5-10HP down on a good DT engine. Your yellow bike sounded a lot like it was bouncing off a rev limiter the times I heard it.You were up against some well sorted packages and that's different to throwing on a trials tyre and riding. 

[bazza]

have a Maicosport and did not cut the frame but used centre port possn for mikuni,305 big bore etc one of my favourite bikes.Saw john Peters in 1991 at Dargyl
went home and made one and raced ever since as reliable as sin.Will try to pm you photo later

[pancho]

XT500 plus good cam plus good piston.

[pancho]

only they probably won't let you ride in pre 75.

[Lozza]

 Dirt track seems to me a bit like road racing , in the run to the first corner is very important and the drive off corners and some top end HP to keep the drive going. I will stand corrected but to me difference is I suppose being able to 'read' the dirt surface and pick where you can get the best drive from(dodging some bumps as well). I would be confident a well set up and tuned 250 2T should be able to mix it with the 4T's.

[Noel]

Hyjack,
Lozza any idea's on making an RD200/DT175 work
Cheers
Noel

[Lozza]

Sure Noel, the RD 200 no worries the DT I would just keep riding that to work

[Noel]

the RD is in the DT frame
Noel

[matcho mick]

ooooh,i know where your'e going with that combo Noel  ,twingle perchance ,

[Lozza]

RD 200?    What did the Northern Beaches throw out turn up something interesting?  A King Kenny style flat tracker is that what you had in mind? 90 deg firing/twingle would work a treat

[suz125]

fork that get an rd400 and water cool that baby, anybody got a good roller I can slip that into?