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Montesa 348


slogger
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After enjoying a full competition on my recently purchased 348, things turned the corner during practice yesterday. Firstly the bike was misfiring under load at about half rev's. I put this down to the incorrect carb fitted and wondered if the jetting / mix was wrong but nothing had changed since the last competition although I was not entirely happy with the performance during the comp but it did run reliably throughout. Then after riding up a rock staircase and going off line on my third attempt, the bike came down with quite a jolt, I ended up in the stream and the bike would no longer start. The bike did not rev out it just ticked over had a very brief increase to about 1/4 revs for a second then died (the bike ended up inverted) and no water got into the exhaust.

Having changed the plugs etc, I can confirm that their is no spark. I have isolated the kill switch so that it is just the black lead out of the flywheel case into the coil and a single coil HT lead to the plug.

If I remove the black lead to the coil and attach a wire with a bulb going to the frame I get a strong illumination. The points are also about .20mm when closed and using the sighting window in the flywheel are opening and closing OK.

When I bought the bike the receipts said that it had a new coil about 2 years ago from Sammy Miller, the brand appears to be WAT YONG? So a few questions:

1) Any other tests I can do to prove that the flywheel element is OK and any other tests of the coil

2) What is an advisable replacement coil

3) Could the immediate deterioration of the electrics be linked to the poor performance earlier?

Am loving the bike but this is a bit of a pain! The bike came with an incorrect carb and I am planning on swapping that but I need to nail the electrics first....

any advise is appreciated. Whilst I am ok with spanners my electrics knowledge is limited so please explain in detail......

Rob

Edited by slogger
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Would also be interested to know how to remove the flywheel and how to check timing, points etc?

Have removed the nut holding the flywheel to the crankshaft but I assume the flywheel either needs a puller or is on a taper / reverse thread??

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There is a tiny woodruff key to line up the flywheel and sometimes they shear and can create the problems you are having by putting the timing out. In any case you are going to need a puller to get the flywheel off. Timing is 1.8 mm btdc and points are set at 16 thou. See how you go

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There is a tiny woodruff key to line up the flywheel and sometimes they shear and can create the problems you are having by putting the timing out. In any case you are going to need a puller to get the flywheel off. Timing is 1.8 mm btdc and points are set at 16 thou. See how you go

Cheers for that. With the timing out, I can understand the misfiring earlier but that was before the off which caused the power loss. The fact that current is flowing from the flywheel out to the tip of the black lead (into the coil) but I am getting no spark when this lead is connected to the coil pack would indicate a problem at the coil pack end ?

Also I have read in other posts about "timing marks". I can not see any on the outer of the flywheel, where would I find them ??

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Sad to tell you, no timing marks on the flywheel and it is really going to be a case of eliminating the problem. Could be a number of things. Condenser like someone has suggested, timing, points, spark plug, coil and even the plug cap? Who knows?? The carb is ruled out because you have no spark so it has to be electrical. I have all the bits and pieces here to find where the problem lies. Only problem I am about over 15000 Kilometres from where you are ! That coil name sounds like some sort of Chinese crap. Have it tested by an electrician and if it is not that get on to the other things I have mentioned. Those 348 motors were really simple to work on and easily fixed and it is really going to be replacing bits until it is going again. Good luck

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Sad to tell you, no timing marks on the flywheel and it is really going to be a case of eliminating the problem.

Only had a brief glance, so my statement was an assumption. What am I looking for both on the flywheel and point of reference to allign it to ??

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That small woodruff key I mentioned earlier is the alignment point. The key sits on the crankshaft and the flywheel has a cutout which fits into that key. Best way to do your timing is to rotate the flywheel until the cam is at its highest and the points have opened and adjust them to 16 thou. You are going to need a dial gauge screwed into the spark plug hole for the next bit. Rotate the flywheel slowly clockwise and keep an eye on the dial. As the piston is on the compression stroke and nearing the top, at 1.8 mm BTDC, the points should be starting to open. Hope that helps.

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Beldane, thanks for all that. Just so I am clear:

1)Timing completed with flywheel on, lined up with crankshaft via woodruff key

2)Points gaps set at point where points are open. Set to 16 thou

3)On compression stroke the points should start to open at 1.8mm BTDC

question, if they open earlier / later, where is the adjustment made if the woodruff key is a fixed point ???

Also, have located a flywheel puller but regarding the dial gauge, all of the ones I can find dont appear to have a threaded adapter for the plug hole ? Is that correct (ie that have and 8mm diameter stem). Have included a link to one for validation ???

http://www.axminster.co.uk/axminster-axminster-dial-gauge-prod21170/

Edited by slogger
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Beldane, thanks for all that. Just so I am clear:

1)Timing completed with flywheel on, lined up with crankshaft via woodruff key

2)Points gaps set at point where points are open. Set to 16 thou

3)On compression stroke the points should start to open at 1.8mm BTDC

question, if they open earlier / later, where is the adjustment made if the woodruff key is a fixed point ???

Also, have located a flywheel puller but regarding the dial gauge, all of the ones I can find dont appear to have a threaded adapter for the plug hole ? Is that correct (ie that have and 8mm diameter stem). Have included a link to one for validation ???

http://www.axminster.co.uk/axminster-axminster-dial-gauge-prod21170/

For a dial gauge and adapter see E-bay (USA), item #140574740657 (BULTACO OSSA MONTESA MAICO MOTORCYCLE TIMING GAUGE TOOL).

Timing requires that both the points and the stator be adjusted. If you have set the points at 0.3 to 0.4 mm (0.012 to 0.016 in) with the piston at 1.8 mm BTDC you are good to go. If you can not obtain the point setting of 0.3 to 0.4 mm (0.012 to 0.016 in) with the piston at 1.8 mm BTDC, then you need to remove the flywheel and loosen the three screws that secure the stator backing plate and move (rotate) the plate in its slotted holes. If the points are too close with the piston at 1.8 mm BTDC, then move the stator clockwise. If the points are too far apart, then move the stator counter-clockwise. All of this involves removing the flywheel each time you change the setting, then re-installing the flywheel and re-setting the points and timing. A bit tedious, but well worth the effort to get it right.

Edited by nh014
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That dial gauge is not going to work because it has to be fixed to the head to give an accurate reading. Have a look at the link from B40RT. If the points don't start to open at exactly 1.8 mmm, you can compensate by setting the points between 15 and 17 thou and that may do the trick. I have found that it makes very little difference. If you can't get the points to start opening between those settings you will have to rotate the stator plate and that is held on by 3 screws but I very much doubt you will have to do that as that stator is held pretty firmly and is not likely to have moved since the bike was running OK.

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All,

Many thanks for the comprehensive advice. Have ordered a flywheel puller and had ordered a dial guage (but not sure if Im going to need it now.....). Did kick it over last night after removing one plug to ease the compression (was kicking it over with both plugs in and a spare plug in the cap to ground). With the black lead connected to the coil I did get a good clean spark !

Am going to strip it all down and check everything incase it has moved on the woodruff etc. Will let you know how I get on !

thanks again

Rob

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Much fun had this morning....more so to learn that fix as for some reason the spark had come back!!!

1) Checked had a spark with existing set up - check

2) Flywheel off (with correct puller)

3) Replaced condenser with new one (after learning how to solder!)

4) Replaced points with new set

5) Spent 30 minutes finding TDC, 1.8mm BTDC, setting the points, discovering that the points close up when you remove the flywheel, setting the points again, taking the flywheel off again, trying to undo the stator bolts (as the points are opening slightly early, realising that the stator bolts will round off on the heads if I dont use an impact screwdriver (so left as is)

6) Making sure everything is tight and routed right under the flywheel

7) Put flywheel on and kicked over - hooray still have a spark

8) Put tank on and kicked it over ............ it started and ran !

Thanks to everyone for your help, I dont think it is 100% but it has been my first attempt and now I have the confidence to press on..

Now onto ebay to look for a new carb !

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Much fun had this morning....more so to learn that fix as for some reason the spark had come back!!!

1) Checked had a spark with existing set up - check

2) Flywheel off (with correct puller)

3) Replaced condenser with new one (after learning how to solder!)

4) Replaced points with new set

5) Spent 30 minutes finding TDC, 1.8mm BTDC, setting the points, discovering that the points close up when you remove the flywheel, setting the points again, taking the flywheel off again, trying to undo the stator bolts (as the points are opening slightly early, realising that the stator bolts will round off on the heads if I dont use an impact screwdriver (so left as is)

6) Making sure everything is tight and routed right under the flywheel

7) Put flywheel on and kicked over - hooray still have a spark

8) Put tank on and kicked it over ............ it started and ran !

Thanks to everyone for your help, I dont think it is 100% but it has been my first attempt and now I have the confidence to press on..

Now onto ebay to look for a new carb !

I suggest you may want to to consider a Mikuni VM 26, set up as follows:

Needle - 5F21

Slide - 2.5

Main jet - 140

Needle jet - 182 N8

Pilot jet - 40

Air jet 0.5

I made the coversion on one of my 348's a couple of years ago and have been well pleased with the performance.

Edited by nh014
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