Montesa Header Restrictor

I got a new header pipe for my 00 Cota. When to put it on today and discovered to my surprise a restrictor plate welded inside! The pipe is about an inch in diameter and the restrictor on the inside cuts that down to about 1/2 inch. It's tack-welded in three spots so I figure I'll just grind the welds down and bolt hit on in from there. Anybody seen a restrictor in a Monty header before? Can't imagine that I'd want to leave it in.

Try it first!

hey john , chad here , does the old one have it in there ?? does sound a little odd , but who knows ??:thumbsup:

it might be there to work sorta like an expansion chamber, or to create back pressure in general. Could also be there to keep it's shape during shipping, but that sounds even more out there. but yea, definatly take a look at hte old one.

I heard that there were a couple of restrictors built into the Montys, which everyone does away with as soon as they get them. At least over here in the UK... I definately remember an exhaust restrictor, and I seem to recall a carb one too, but I'm unsure as to what that is exactly.

Does your old header have the plate in? Or the remains of the spot welds maybe?

I say get rid...... :thumbsup:

I heard that there were a couple of restrictors built into the Montys, which everyone does away with as soon as they get them. At least over here in the UK...

That was for the 4-Stroke Montesa. I've never heard of anyone doing it with the 2-stroke.

And yes... Back pressure at the right location and in time with the ports is an important part of producing the smooth strong torque of the Trials 2-Stroke.

I would definitely check with a dealer that works on them regularly.

The restrictor plate is NOT in the one I took off. I'll post a question to trials central also. Lot's of British monty guys over there. Higher back pressure does aid in low rpm scavenging. And tighter exahust definitely improves low end torque in four strokes. Can't image how it could possibly help on a two-stroke.

Look at any 2t motocross pipe. They really taper off before the silencer... Maybe that's what it is.

And you still haven't told us: does the old exhaust have the remnants of spot welds on the inside???

Do monty's have a middle silencer like on the GG's? If they don't then that would deffinatly be the purpose of the restrictor...

Forget all of the forum stuff though- just call a dealer. You will have you answer is 5 minutes......

Couldn't find the remains of any spot welds on the inside of the old one, however it was pretty well carboned-up and I may have missed them. I think cleaning the carbon off would probably scuff the pipe to the point where I couldn't tell if there were ones there before. And the old one had no inner baffles of any kind.

TrialsCentral reports it as one of three restrictor plates that came on the bikes when new and that it should be removed. So, I ground the welds down and pulled the restrictor. I installed the new pipe and fired the bike up. I noticed an immediate change over the old pipe which was squashed in one place about 50%. The exhaust note was much sharper, more like my old GasGas. The Monty had always sounded a little soft.

Then I rode it. I couldn't tell much difference over the old pipe at low RPM. At high RPM the difference was significant. With the old Monty it always felt like it was trying to go faster but couldn't. Like it was tired. Not lugging so much as just not responding. That is gone. I decided not to try it with the baffle in first since I only had one exhaust gasket. It was a squash type gasket and never works as well the second time around.

john,like yz said.youll get a more straighter answer from a dealer.talked to one,header restrictor, remove,theres one in the midpipe,take it out.the air box,take it out.this fact ,not a bunch of hunches.yamaha corks the shit out of the wr's as well to get them overseas.

Fester, thanks.

I once owned a WR. Lovly suspension. And great bike after you uncorked it. Never did love the powerband even then, though. Always had to wind it out to get any power. Guess I'm a trials guy at heart.

earth to john,did you check the mid pipe and the air box,i dont know what wr you had but my 426 just out and gets it on!

earth to john,did you check the mid pipe and the air box,i dont know what wr you had but my 426 just out and gets it on!

250. Oh, it would fly. But I prefer low end torque and it didn't have any.

Take it out. Those were in there for euro sound laws. all the montys had them but they were removed by the dealer before delivery.

Good call obwon. I brought in a handful of the 2 stroke RTL honda's,late 90's, and they did not have the restrictors that the mantossers came with and I concer that they were for sound requirements. I believe I still have a Dealer set up for the 315R somewhere and it stated to remove all restrictors......IF yoiu want moped power you could leave it in. Had a GASGAS 50cc SM with exhaust restrictor what a difference when it came out!!!

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