reed valve mont cappras

[montman]

Just wonderd if anyone has converted a 250/414 cappra to reed valve and if so how and was it any good.

[All Things 414]

It'd be a pointless exercise. The biggest thing I've learnt from my time in VMX and especially with the Montesa's is that the engineers actually had an idea of what they were doing. Especially when it comes to cylinders, porting and pipes. Once you start screwing with them you throw the balance out and lose the magic of these great bikes. Usable power, great handling and a bit of harmony.
When I first started out I was changing this and that and trying to improve things and begrudgingly, at the end of the day, I had to admit that things were no better.....
So now my motto is
"If you want them to rock, leave 'em stock".
Leave that sort of thing up to the Maico 490 and Honda guys......

* On the advice of a race tuner and engine builder whom I implicitly trust, I have a poofteenth taken out of the heads of my bikes to lower the compression due to the low octane that we run today in fuels.

[mx250]

I like Ross's advice. I think it is particularly applicable to Monties. Monties were designed and set up for European MX - either deep sand tracks or muddy tracks. In these situation a stable but quick turning, easy steering bike with lots of mid range excels.

My understanding is that reed valves add bottom end and mid range to what would otherwise be a high hp high revs piston port engine. If a piston port engine is a grunt master I can't see putting reeds on is gunna change anything. If things change it would probably be to the determent as the reeds interfere with the airflow.

Lozza will be along in a mo and tell you 'go for it' . But then he'll say 'you just have to open up this port here, lift the exhaust port, increase the transfers here, here and  here' etc  .

You'll probably produce more hp (and suck more juice) but if you produce more useful hp will probably be argumentative or dependent on where you ride.

[cappra]

Amen, brothers.....

[Lozza]

Just wonderd if anyone has converted a 250/414 cappra to reed valve and if so how and was it any good.

Depends how it's done. When completed correctly the reed engine will have more and a far better spread of power.Very helpful in preventing spit-back or reverse flow into the carb.Just post a pic of the cylinder.

I'll leave you with the words or Ramon Forcada, if you got to ask he's Jorge Lorenzo's crew chief, he started  with Eduardo Giro at Ossa and went through working on every fast Spanish two stroke ever built and with just about every fast Spanish rider that ever raced(and a few others).His words still ring in my ear when he stated 'Even on a GP level factory bike I see things that can be improved"
Ramon spends his 'spare' time prepping enduro and supermoto bikes.

[firko]

Despite Ramons wise words, I agree with my learned colleague yet again.... but from a Maico perspective.
Back in the early vintage days I tried to perfect the reed valve conversion on Maicos. I tried modifying a Gem reed with no obvious improvement then adapted a Yamaha MX250 reed block to the Maico barrel. It took many hours of welding and porting and reed material trial and error but the end result was that the engines performance improved two fifths of FA. I now run them basically stock, even down to using Bing carbs. The only major mods being a more modern pipe design and PVL ignition. As Gary Treadwell ( a tuner who knows his shit once told me, "some engines work better the way they were created, Maicos don't seem to respond to reeds". It seems Montys are in the same boat.

[mx250]

As a wise head once told me; if you want hp on a 4t concentrate on the inlet side; if you want hp from a 2t concentrate on the exhaust side. . 

[All Things 414]

Yes at GP level I'm sure there's room for improvement in my engines but I'm a long way off being a GP rider (except when I've got Black Sabbath's Neon Knights pumpin' out the stereo and no one's home )

On the track I was racing on last Sunday there's a step-up jump just out of a corner which you have to be gassin' it to make the leap. At first I was shifting from 2nd to 3rd and making it easily but the thought of finding one of the many neutrals in my gearbox dictated that making that gear change was going to be folly when I hit the ramp in neutral sooner or later. So....
I decided to leave it in 3rd gear through the corner and hope it would come on the pipe when I hit the jump. With just a hint of clutch when it straightened up and the roar of something close to primal I was happily soaring through the air again.

That's the sort of power a lowly C grader like myself needs on a race track.

Not a time bomb that won't track or steer where I want it to.......

[Freakshow]

Hey 414, when you say a pooftenth out of the head, i think you'd be upping the comp not lowering it.
or are you messing with the squish and shape to create more volume in there ?

[cappra]

No doubt that almost any motor can be improved if you throw enough money and time at it. 
Big bore Montesa's seem to have plenty of power without the addition of reeds.  In 1974,
EC Birt, the reed valve master, tried to make a Rickman VR 250 faster with the addition of
extra boost ports in the piston, a reed setup and custom pipe.  On the dyno, the stock
motor produced 26.5 hp at 7,850 rpm (rear wheel)  With the reed setup 28.4 hp.  He did
say at the end of the article "To improve over the stock Montesa engine is very hard to do
and it should not be messed with unless you really know what your doing.  So ride it!
With this kind of horsepowe curve, you can win with it stock"

[cappra]

I have taken a 414 cylinder to the local go fast guy who had
computer controlled air flow testing equipment and he does work
on modern mx and flat track bike.  He took one look at the 414's
transfers and the intake tract and just rolled his eye's and wondered
how the bike even ran.  Just told him that it's the combination that counts.

[All Things 414]

or are you messing with the squish and shape to create more volume in there ?

Yeah Freaky. He gives the head a little more volume (takes some out of the dome). I've had him to it with my 2000 YZ as well.

[Freakshow]

interesting, i have only heard of guy decomping a motor to run off hot events, such as long flat out racing like dirt track and enduro stuff.  NEver seen it on mx type on/off throttle events. 

might have been cheaper just to add another base gasket ........... 



PS...do the nanna party dance  Nimmo,  you know you want to........ 

[All Things 414]

It has to be your most annoying avatar yet......

[Freakshow]

Success !!!!!!