montesa cota mh 349 help needed

[dr770]

Well finally first ride!!

a few things still needs to be sorted . even with new seals, fork is leaking little bit, clutch oil is leaking , need a front fender , but it starts very easy at firtst kick. 

This was the first time I have ridden a trials bike, it feels very light and fun. the engine is strong and seems un stoppable. I need some time to get rid of clutching addiction.

I am open to any advice and experience.

 

Thanks

[fourex]

On 03/08/2017 at 5:31 PM, dr770 said:

Update;

The air filter sorted out. The points gap is set and it starts at the moment. But i should say it is really difficult to start with tons of compression. Is there an easier way?  I have already trashed 2 shoes :-) 

The front suspension was not working properly, so i took it apart.as soon as i see from the diagram there are 2 parts under the circlip. One is the seal the other is the bushing i guess. Well the bushing is missing:-( on both legs. There are 2 part codes there. C000.993547 which i think the seal and 0CM1.35037 (seen on the diagram below) which i think the bushing.i have purchased the seal 6x35x47 mm dimensions,  but i couldn't find any information about the bushings. I am about ti machine them out of some kind engineering polimer. But a proper picture would be helpful really. so I can machine out a similar one 

Thanks

I've attached the page from the MH 349 parts manual showing the fork internals, looks to me like only 1 seal per leg and no spacers. It's the same in the 349/4 and 350 manuals I have also. No extra threaded hole in the head for a decompressor on any of these models.

 

 

Edited September 21, 2017 by fourex
changed attachments from pdf to jpeg.

[dr770]

3 hours ago, fourex said:

I've attached the page from the MH 349 parts manual showing the fork internals, looks to me like only 1 seal per leg and no spacers. It's the same in the 349/4 and 350 manuals I have also. No extra threaded hole in the head for a decompressor on any of these models.

 

 

Thanks for your help. I dont have the original parts manual for MH 349. it would be great if you can share that one with me. At the moment I could make the fork function by manufacturing custom spacers under the seals. Without these spacers the fork tubes rub againgst the fork outer aluminum lower tubes under compression and this makes great friction. May be this problem is becouse I am using aftermarket seals. these seals can not hold the stanchions co axial with lower tubes, so with hard plastic spacers stanhions is held in place and on the same axis with the loer moving part.

[fourex]

I've sent you a PM. I don't know what is wrong with your forks but from your last post it sounds like they could be bent, the shiny chrome stanchion part is what I'm referring to. 

[dr770]

1 hour ago, fourex said:

I've sent you a PM. I don't know what is wrong with your forks but from your last post it sounds like they could be bent, the shiny chrome stanchion part is what I'm referring to. 

I have measured the straightness , there is no problem. the diameter of inner down tubes are around 1mm larger than the stanchions, so there is fair amount of play without the spacers I fabricated. difference in dameter makes the stanchions touch the outer tubes on 2 points instead of a large surface, under braking especially. My theory this 2 point contact is not enough for the oil film to hold on and as a result the chrome coated tube scrubs the aluminum housing creating a big friction, if I could explain. when the fork is taken away and pushed down on a straight line wit 0 bending moment it works just fine , but under braking force which creates a bending moment it just locks itself. What ever it is with the custom spacers and narrover seals it is working now ( like each of the forks on other bikes have).

The spacer is keeping the stanchions on the same axis and preventing the play on the down tubes.May be the forks was used without oil inside for a long time and this ruined the setup. hope my solution lasts long enough to have some fun for this winter.  

[dr770]

Hello;

I want to ask a question about the number 5 part on the exploded view above. is it normal to have a very tiny hole on it which enables the fork breathe in-out during travel? I hve never seen thhis before, many mx bikes have bleed valves or screws but this is completely open to the atmosphere. And yes there is oil leaking a bit under full compression landings.

Thanks.

 

[b40rt]

Block it and see what happens, will increase spring rate slightly.

[dr770]

1 hour ago, b40rt said:

Block it and see what happens, will increase spring rate slightly.

yes I know but I was affraid that this will increase the air pressure inside and lead to sealing failures. Actually I think the fork spring rate is too soft for my taste, is it common for twinshock trial riders to put some spacers under springs?

[b40rt]

1 hour ago, dr770 said:

yes I know but I was affraid that this will increase the air pressure inside and lead to sealing failures. Actually I think the fork spring rate is too soft for my taste, is it common for twinshock trial riders to put some spacers under springs?

Yes, it will increase air pressure as you say, but "shouldn't " lead to seal failure. Preload / spacers are common, trial and error to get it right, I have a bout 50mm in marzochi's.  Spacers obviously won't change the spring rate, but will affect sag, also consider thicker oil, 7.5 / 10 fairly common starting point.  (Auto trans fluid is about 7.5)

Chances are the springs are past there best, might be worth replacing them.