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Mh349 Rebuild


jimbo349
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Ok I have started to strip my mh349 down and assess whats required, I have owned this bike from new and used it for trials and for general nobbing about the countryside. I has seen little use in the last 15 years apart from a handfull of trials about 8 years ago. Its been buried in the shed since and has deteriated shamefully in that time. It still has the origional cables, front tyre, paint, chain and front sprocket the rear being changed from 33 to 38 tooth when only a few weeks old.

So it needs;

The frame and exhaust painting

The engine rattles on overrun and the piston is quite loose in the bore so I guess a rebore will be required soon although the compression is still bloody good . It had a small end 8 years ago from sandifords when I did a few club trials.

Parts required (any suggestions on the best vendors would be appriciated)

Complete set of cables

Chain and sprocket set I think the front is on a taper and not the spline as its held on with a 24mmAF nut (any input would be nice)

Rear shocks or replacement rubbers

Rear brake cable this snapped years ago and was replaced with a rod which works but not correct.

Carb rubbers both sides

1 Chain tube

Chain tentioner pad

Airfilter

Front tyre and tube

Fork seals

Fuel tap leaks Sandifords could not provide a replacement 8 years ago and as a temporary fix greasing up the rubber sorts it for a few months.

LH fork slider as the lug for the brake torque arm has snapped off or someone to build it back up with weld. The front wheel was reversed as the LH slider has the same lug on the rear of the slider.

The wheel hubs are requiring paint and in time I would like to have the wheels respoked and refurbished.

The clutch slips in 5th and 6th and will require new plates but I may play with oils first always used ATF.

And a bit lump of TLC.

So guys who's the best company for the above.

Thanks in advance James

Im in the UK BTW.

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The twinshock shop will be able to do everything mentioned, google them for the website, i have seen one of the bikes that they turned out and i am very impressed!

Just a quick note on your forks, if the lug is broken on one side and you want to fit the wheel as it should be, clean up the broken lug, grind flush etc and simply swap the forks over in the yokes?

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Venhill are probably the only cable supplier now. You can order direct from them but MAKE SURE you measure your front brake and clutch cables before you order from them as you may well find that their front brake cable is too short unless they've corrected it since I ordered one. They also had a bit of a mix up between 242, 330 and 350 part numbers (their part numbers that is) Better still, send the old cables to them so they can ensure they send you the correct ones back with the correct nipples either end and the correct adjusters.

for the parts below, In Motion (Bultaco UK) should have them all

Chain and sprocket set I think the front is on a taper and not the spline as its held on with a 24mmAF nut (any input would be nice) - Yes it is on a taper, the original also has a slot for a key but the replacement Talon one doesn't but the tasper is sufficient. Have fun getting the old one off...

Rear brake cable this snapped years ago and was replaced with a rod which works but not correct - They have the cables for the 247 Cota so should have the MH349 too but a rod is probably better

Carb rubbers both sides

1 Chain tube

Chain tentioner pad

Airfilter

Fork seals

They will also have the cables but obviously these are from Venhill and are what Venhill send them. I'd get them direct from Venhill so you can make sure they are correct.

They may have a fuel tap also.

If you search the Montesa or Twinshock forums you should find some advice on the MH349 clutch set up from Rob Taylor who rides one regularly and who very kindly lent me one to ride in the Bootle Classic trial after I broke my Ossa the day before.

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Here is the clutch info Woody mentioned, some more has been added as well.

If your clutch slips when kicking the bike over or when pulling a big gear this is not unusual. The MH349 has an all metal clutch which does not seem to like modern synthetic oil. It may be worth changing the oil before going to the expense of new clutch plates. Following advice from Kevin Breedon Racing we have used 300 cc of an old style straight monograde oil in the primary drive case. Morris Lubricants Golden Film SAE 20 is available direct from the makers in 5 litre containers. To be sure there were no additives left over from the modern oil we changed the first fill of monograde after only a few hours use. With the monograde oil the clutch does seem a lot better. The 349 produces a lot of torque and the clutch is only small so it will always have a hard time when the bike is used fully.

We also use genuine Amal clutch and brake levers, they seem to give the best all round leverage for the clutch to free off without being too heavy in action. The Amal levers are tough and a bent lever blade can be straightened with care.

A Venhill Featherlight clutch cable also helps lighten the action, keep the cable lubricated as Venhill's instructions and keep the lever pivot greased also.

The 24 mm A/F nut on the gearbox sprocket has a left hand thread.

We have used a 10 tooth gearbox sprocket with either a 40 or 42 tooth rear wheel sprocket and this seems to suit the more modern sections.

For a petrol tap contact Steve Goode Motorcycles, Steve sells a two bolt flange mounting OMG tap which will fit the MH349 tank. The exit from the tap wants to be from the bottom so it does not foul the frame when you hinge the tank up.

Hope this helps.

Here is a link to Woody in action on the MH349

Edited by Tayld
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  • 1 month later...
Here is the clutch info Woody mentioned, some more has been added as well.

If your clutch slips when kicking the bike over or when pulling a big gear this is not unusual. The MH349 has an all metal clutch which does not seem to like modern synthetic oil. It may be worth changing the oil before going to the expense of new clutch plates. Following advice from Kevin Breedon Racing we have used 300 cc of an old style straight monograde oil in the primary drive case. Morris Lubricants Golden Film SAE 20 is available direct from the makers in 5 litre containers. To be sure there were no additives left over from the modern oil we changed the first fill of monograde after only a few hours use. With the monograde oil the clutch does seem a lot better. The 349 produces a lot of torque and the clutch is only small so it will always have a hard time when the bike is used fully.

We also use genuine Amal clutch and brake levers, they seem to give the best all round leverage for the clutch to free off without being too heavy in action. The Amal levers are tough and a bent lever blade can be straightened with care.

A Venhill Featherlight clutch cable also helps lighten the action, keep the cable lubricated as Venhill's instructions and keep the lever pivot greased also.

The 24 mm A/F nut on the gearbox sprocket has a left hand thread.

We have used a 10 tooth gearbox sprocket with either a 40 or 42 tooth rear wheel sprocket and this seems to suit the more modern sections.

For a petrol tap contact Steve Goode Motorcycles, Steve sells a two bolt flange mounting OMG tap which will fit the MH349 tank. The exit from the tap wants to be from the bottom so it does not foul the frame when you hinge the tank up.

Hope this helps.

Here is a link to Woody in action on the MH349

Good advice thank you.

Work on the bike is coming on slowly but this is where I am at the moment.

Clutch was shot so a new one is fitted with new springs.

The piston is quite worn but will have to fly for now a mahl piston is nearly

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The fork stanchions fitted to the MH349 and the 1982 and later Cota 349 are longer than those used on earlier models. The 242 has the same stanchions as the MH349. As well as the stanchions the sliders are also longer than the earlier bikes, the increased length is above the mudguard bracket.

We have not had any luck in getting good used stanchions. If your own stanchions have poor chrome but are free of rust inside the tubes it is probably worth considering having them rechromed. We have had a pair done by Philpotts, they are now back in the bike and working well again. The tops of our stanchions (without the cap nuts) are set 6 mm above the top yoke, this gives good steering when used with 360 mm long modern Betor rear units fitted with 50 lb springs.

Hope this helps.

Edited by Tayld
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The fork stanchions fitted to the MH349 and the 1982 and later Cota 349 are longer than those used on earlier models. The 242 has the same stanchions as the MH349. As well as the stanchions the sliders are also longer than the earlier bikes, the increased length is above the mudguard bracket.

We have not had any luck in getting good used stanchions. If your own stanchions have poor chrome but are free of rust inside the tubes it is probably worth considering having them rechromed. We have had a pair done by Philpotts, they are now back in the bike and working well again. The tops of our stanchions (without the cap nuts) are set 6 mm above the top yoke, this gives good steering when used with 360 mm long modern Betor rear units fitted with 50 lb springs.

Hope this helps.

Thanks for that I guessed the travel was longer my bike always ran with the forks 6mm above the yoke from new, must have been doing something right all those years ago.

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  • 2 weeks later...
 
  • 3 months later...

11th hour problem

Got the bike 99% done but the clutch is giving me some problems.

New plates and springs from Inmotion filled with the correct quantity of ATF but the clutch wont hold enough to start the bike with the kick starter it just slips. The basket is fine with no steps on the contact points and the cable is slack with free play on the clutch arm so the clutch is fully engaged.

~Just running this by you guys before i contact Inmotion for advice.

The original clutch was better!

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  • 1 month later...

Well the bike is now done in readyness for a clubman trial on sunday, the clutch is sill not 100% but im hoping it will improve. I dropped the ATF and filled with a basic mineral 10/30 (I had some) as per the manual the clutch does not slip like it did on the starter but drags a little. I will take some pics and post them up tomorow.

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Well the bike is now done in readyness for a clubman trial on sunday, the clutch is sill not 100% but im hoping it will improve. I dropped the ATF and filled with a basic mineral 10/30 (I had some) as per the manual the clutch does not slip like it did on the starter but drags a little. I will take some pics and post them up tomorow.

Happy New Year Jimbo, really looking forward to the pics.

All the best,

Carl

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  • 4 weeks later...
 

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