Ossa 250mar Misfire

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Black111r
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Ossa 250mar Misfire

Postby Black111r » Mon Sep 19, 2011 2:14 pm

Hi

I am posting below a link to Trials Central Forum where i have been discussing a misfire problem with my Mikuni jetted Ossa

http://www.trialscentral.com/forums/top ... ntry280163

Does anybody here have any thoughts as to where to go next with this.

Is it the coil that I should be looking at next?

Thanks in advance for any comments/suggestions

Chris



Black111r
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Re: Ossa 250mar Misfire

Postby Black111r » Mon Sep 19, 2011 4:24 pm

Following advice i took a deep breath and have put the old Amal back onto the bike to see if I can isolate the problem.

Just to spite me the bike started first kick! However after running for 3-5 mins (as before) it started to misfire in exactly the same manner as before.

I took the chance to inspect the rubber inlet spigot hose- it was perfect with no splits or deformity in the spigots.


Pulling the plug this time, however, did show a lot more oil so it would suggest that the new Mikuni carb is helping the fuel to be burnt more efficiently.


But back to the misfire.

Should I replace the Motoplat with a new coil or just replace the condenser. Which is the most likely to be causing the problem?

The HT lead does show signs of being burnt against the exhaust however I have shielded these areas with hose so I do not think that it is shorting. in fact the lead has always been like this so i do not think that this is the cause of this misfire.

It is also sealed into the Motoplat so replacing it will mean a new Motoplat coil.

Any thoughts


Chris



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Re: Ossa 250mar Misfire

Postby Bully fanatic » Mon Sep 19, 2011 5:09 pm

Hello black11ir. Does your Ossa have points in it, if it does then yes replace the condenser because missing is a sure sign of a dodgy condenser. Easy`st way is to use a car one of a similar size which is also a lot easier to get hold of and a lot cheaper and if it has points then plug gap is important as well, the Bultaco`s like a plug gap of .40 mm the same as the points so check it is at Ossa`s specification. I hope this helps. Graham.



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Re: Ossa 250mar Misfire

Postby Bully fanatic » Mon Sep 19, 2011 5:19 pm

Chris, me again I forgot to say to put the condenser up under the fuel tank usually on the coil mounts is a good spot as it helps to keep the condenser cool. With the spark plug lead you can replace the lead by cutting it off close to the coil and soldering another copper lead on and use silastic on the join with heat shrink over the top to seal everything or just use heatshrink on the old lead to seal it up. Graham.



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Re: Ossa 250mar Misfire

Postby Black111r » Mon Sep 19, 2011 5:29 pm

Hi

Thanks for the feedback.

Okay

Tomorrows job is to have a look at the points/condenser.

Can anyone here confirm whether the ossa 250mar mark 2 1975 has points (think they do) and what is the correct condenser that I need to use? Any local suppliers or does anybody have one

Also I understand that the flywheel has to come off to access the condenser. Any thoughts on whether the nut is right or left hand threaded and whether I need a special tool to pull the fly wheel.

On that note, if so does anybody have one I can use?

Doesn't stop does it!


Chris



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Re: Ossa 250mar Misfire

Postby David Lahey » Mon Sep 19, 2011 9:05 pm

Chris you probably only have to post on either the Aussie forums or the Trials Central forums because the same people read both. I've just posted a reply to you on Trials Central about your ignition.
Pullers for OSSA motoplat flywheels are available from the UK or if you are happy to pay the postage I can post you mine and get it back off you at Conondale.
David Lahey


relax, nothing is under control

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Re: Ossa 250mar Misfire

Postby David Lahey » Mon Sep 19, 2011 9:16 pm

Chris I've just remembered my wife is going to Brisbane this weekend so the puller could be collected from Sheldon from Sunday afternoon onwards if you want


relax, nothing is under control

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Re: Ossa 250mar Misfire

Postby Black111r » Mon Sep 19, 2011 9:20 pm

hi David

Any thoughts on a quick source of condenser. Andrew mentions using an old VW one. I assume a 6v one?

I can get the condenser, puller and new set of points from In-motion UK but this will be another week. If I can find a condenser locally then will happily borrow your puller. I can collect from Sheldon and either post back or pass to you at Conondale as you suggest

I will let you know how I get on

Thanks


Chris



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Re: Ossa 250mar Misfire

Postby David Lahey » Mon Sep 19, 2011 9:25 pm

Condensers are for motors with points and the OSSA MAR Mk2 does not have points. Please read the posting on Trials Central


relax, nothing is under control

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Re: Ossa 250mar Misfire

Postby Black111r » Mon Sep 19, 2011 9:33 pm

Just read it!

Will investigate tomorrow

Thanks

Chris




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