montesa cota mh 349 help needed

[collyolly]

No, the points gap should be set once it has been opened fully by the cam on the back of the flywheel, then you set the ignition timing by rotating the crank up to top dead centre, finding the position of 2.7mm before top dead centre (BTDC) at which point the points should just be opening hence the use of a 'piece of fag paper' 

The fag paper or Thou feeler gauge is held in the closed points and as you adjust the position of the points backing plate to adjust the timing the correct position is when the fag paper is released, this is when the points are just being opened by the cam on the back of the flywheel

Hope that makes sense !

[dr770]

54 minutes ago, collyolly said:

No, the points gap should be set once it has been opened fully by the cam on the back of the flywheel, then you set the ignition timing by rotating the crank up to top dead centre, finding the position of 2.7mm before top dead centre (BTDC) at which point the points should just be opening hence the use of a 'piece of fag paper' 

The fag paper or Thou feeler gauge is held in the closed points and as you adjust the position of the points backing plate to adjust the timing the correct position is when the fag paper is released, this is when the points are just being opened by the cam on the back of the flywheel

Hope that makes sense !

Very well understood,  thanks. Actually this was what i came up first but then i read a little more and became confused. Its all clear now. I was thinking to adjust by using a battery, some cable and a lamb and using the points as a circuit breaker of the lamb. I guess this will also work.

[cleanorbust]

Yes, I have also used a bulb set-up in the past to determine when the points are opening. Probably more accurate than the paper method. As an easy first step you could try just setting the points to the correct gap when they are fully open if they aren't already and seeing how it runs then. Points can tend to close up which retards the ignition and results in poor response from the engine.

[bullylover]

No. That means that the points gap should be 0.4mm and the points should start to open at 2.7mm BTDC. I always use a multimeter on OHMs to check when they start to open. Just use the wire from the points up to the coil and put on end of the multimeter on that and the other end in a bolt hole on the engine or anywhere you can find that is a good earth and that will tell you exactly when the points are starting to open.

[dr770]

Hi Here are few more pics. I couldn't stop myself from taking it apart.

It has a broken air box, but luckily ex owner put a kone filter in there bit with a narrow connection about 30 mm

Exhaust is leaking heavily from the silencer inlet 

Take one of the shocks apart. See it can be rebuilt. The valf spring inside is broken. Not sure if the seals are ok. I really need some information on rebuilding these shocks. 

The fork isn't feeling ok. I couldn't find a clue it is bent, but it doesn't operate smoothly,  any info on rebuilding these?

Someone has been played.with electrical system. The book i jave.states that cota is 6v system but this one seems to be 12. There is a rectifier and some.relays for headlight and horn. I want to get rid of them anyway but affraid to ruin something before undetstanding what is what

Front brake pivot tread is completely gone, i should retap it with m12 i guess

That's all for now....

[cleanorbust]

Stripping the forks should be fairly straightforward. You'll have to unscrew the allen bolt in the bottom end of each slider, holding the internals to stop them spinning as you turn the bolt. Be sure to fully unweight the front end when you unscrew the fork caps  (bike on a box or stand with wheel off the ground) as they have very fine threads which can get damaged if there is much pressure on them from the fork springs just before they come to the end of the thread.

[dr770]

20 minutes ago, cleanorbust said:

Stripping the forks should be fairly straightforward. You'll have to unscrew the allen bolt in the bottom end of each slider, holding the internals to stop them spinning as you turn the bolt. Be sure to fully unweight the front end when you unscrew the fork caps  (bike on a box or stand with wheel off the ground) as they have very fine threads which can get damaged if there is much pressure on them from the fork springs just before they come to the end of the thread.

Thanks, where can i find info on refurbing rear shocks. Searching the web for hours but didn't cone by a shock with similar internals. I think this is a twin tube design but base valf system seems to be located on the damping rod :-( i am confused.... 

[2stroke4stroke]

Could be a non-standard coil, that metal plug cap is definitely not original.

Gearchange mechanism can be fragile - I'd raise the gear lever to avoid hitting rocks.

Posssibly Marzocchi rear suspension? Bits for rebuild should be obtainable even though they stopped making motorcycle stuff a couple of years ago.

It won't run at its best with the altered air filtration arrangement, this might be part of your problem.

[dr770]

22 hours ago, 2stroke4stroke said:

Could be a non-standard coil, that metal plug cap is definitely not original.

Gearchange mechanism can be fragile - I'd raise the gear lever to avoid hitting rocks.

Posssibly Marzocchi rear suspension? Bits for rebuild should be obtainable even though they stopped making motorcycle stuff a couple of years ago.

It won't run at its best with the altered air filtration arrangement, this might be part of your problem.

I have inspected the shocks again, they are betor shocks. The cap is not plugged it is treaded which is good. The seals are far gone and internals seems to be ok except a spring. But i can make new springs, no problem. Will try to find oil seals.

Air filtration is terrible, there is only 25 mm air passage behind the cone filter. This can lead to wrong operation of air correctors. There is big repair on fuel valve on the gas tank. The threaded inserts in the plastic tank came out.The air filter box had a big hole. I am repairing them at the moment but i can't share more pics i think there is a limit which i wasn't aware and i have used it all by mistake.

The engine seems to be picking up fine but then it loses power when i am expecting it to kick in. After air filter system is ok i will try to deal with the timing.

I hope the needle jet is in good shape, that will be difficult for me to source one.

 

[dr770]

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

Edited August 3, 2017 by dr770

[dr770]

1 hour ago, oni nou said:

Fit a decompressor to the cylinder head?

thanks for your feedback. I've been thinking about it but machining will be necessary, this involves the removal of the cylinder head. I have never used a decompressor before and I dont know how to use it. So I could not be sure about the benefit. I know that it will relase the compression, but is it only for taking the piston to tdc? or can I kick start while pulling the decompressor?  

[feetupfun]

If you use the type of decompressor that resets itself, you set it to the open position using a knob on the end of it, move the piston to the right spot, kickstart the bike and it then closes itself.

There is also a type of decompressor that has a handlebar lever so you can open it while easing over TDC, kicking it, and for braking effect while riding.

Are you sure your head doesn't already have a hole for a decompressor? It was fairly common back then to have a decompressor hole.

Cota 349s do take a lot of effort to kickstart. I have a 348 which is only 310cc and kickstarting it is usually the most tiring part of riding a trial and 349s are even harder to kick over. It would be good to just leave it running all day but it is fairly hot here and they overheat if you leave them idling for too long.

[feetupfun]

As for your fork seals, if you can, just buy seals of a width that takes up the space between the seat and the circlip. That spacer in the parts diagram is not a guide for the fork tube, it is just a spacer. Two narrow seals per side or one wide double-lipped seal per side will do the job of sealing the forks. The fork tubes are held centrally in the seals by the precision-machined bores of the sliders.

If you are really determined to make plastic spacers for the fork seals, just make them the right width so that the circlip just touches the top of the seal.

Bear in mind that a couple of my old Spanish trials bikes have no circlips on top of the fork seals and I have sealed up the vents in the fork caps and I run enough oil to firm up the last bit of fork travel using internal air pressure, and those fork seals have never moved out of position. From memory I think the seals are double-lipped and 10.5mm wide.

[dr770]

2 hours ago, feetupfun said:

If you use the type of decompressor that resets itself, you set it to the open position using a knob on the end of it, move the piston to the right spot, kickstart the bike and it then closes itself.

There is also a type of decompressor that has a handlebar lever so you can open it while easing over TDC, kicking it, and for braking effect while riding.

Are you sure your head doesn't already have a hole for a decompressor? It was fairly common back then to have a decompressor hole.

Cota 349s do take a lot of effort to kickstart. I have a 348 which is only 310cc and kickstarting it is usually the most tiring part of riding a trial and 349s are even harder to kick over. It would be good to just leave it running all day but it is fairly hot here and they overheat if you leave them idling for too long.

There is a blank space for the decompressor but it isn't drilled and tapped. As soon as I know older ones have the place for it. This is MH 349. The only type of decompressor I could find are the ones for hacksaws I think they can be used instead . I had a KTM 400 SC and it realy starts much easier. I will try to do my best on ignition and carburetor and wait and see how it performs on kick start. Or I will carry a rope to tie it to my friends bike for a running start   

Keep it idling is out of practice its already 35+ degrees here. My biggest fear was the starting of this bike since my right ancle has problems, Ktm is a left kicker.

 

Thanks 

[dr770]

2 hours ago, feetupfun said:

As for your fork seals, if you can, just buy seals of a width that takes up the space between the seat and the circlip. That spacer in the parts diagram is not a guide for the fork tube, it is just a spacer. Two narrow seals per side or one wide double-lipped seal per side will do the job of sealing the forks. The fork tubes are held centrally in the seals by the precision-machined bores of the sliders.

If you are really determined to make plastic spacers for the fork seals, just make them the right width so that the circlip just touches the top of the seal.

Bear in mind that a couple of my old Spanish trials bikes have no circlips on top of the fork seals and I have sealed up the vents in the fork caps and I run enough oil to firm up the last bit of fork travel using internal air pressure, and those fork seals have never moved out of position. From memory I think the seals are double-lipped and 10.5mm wide.

I could not find a suitable seal which the space could take two of them. I will try to use one seal with single lip and see the result. This is what I can find at the moment and I want to ride the bike on September. I ve got soooo litle time toooo many projects  

I will definately make them in size with the seal which has 47x35x6mm dimensions.

By the way I can't say the bores of the sliders are precision machined unfortunately. The fork tubes are 35mm but the bores are 36. and at the current stage the forks was moving realy stiff after a few cm. And the only thing I could find is the missing spacers. Actually I will check again for a bent tube before installation, I could make it straight if there is any bent part.

 

Thanks for all your information.