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Poor running problem (B175).
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Mannanan
Leigh On Sea, Essex. Uk.
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October 29, 2017 - 9:07 am
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Having convinced myself the reason for poor starting and running was the carburettor pilot circuit, I spent most of the summer with the carb on and off trying to improve things. At the back of my mind was always the question of perished crankcase seals as the bike had been standing for some years. What threw me a bit was no oil mist on the points, no excessive smoke or anything definite to scream seals. The biggest pointer was difficulty starting, impossible to get regular tick over and need for half choke just to run. All of those symptoms could also be relevant for a blocked pilot jet. Finally split the cases yesterday and left in no doubt ...... it’s the seals! Hard perished rubber that almost disintegrated in my fingers. The primary side was twice as badly perished as the flywheel side. Amazed it every actually started at all. Oh well I may have missed summer but there is always next year and by the time it’s all back together, I won’t need to worry about an MOT.

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nickjaxe
Runcorn Cheshire UK
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October 29, 2017 - 9:30 pm
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Good work...hope you sort it soon.

I fitted the slightly more expensive Viton seals.

Nick.

My Bantam video              https://www.youtube.com/watch?v=jjpOFmzRZRI

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Mannanan
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October 29, 2017 - 9:33 pm
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Yes Nick, that’s what I am fitting, full set of seals from Rex around £15.00 which I think is excellent value.

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nickjaxe
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October 29, 2017 - 9:36 pm
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Did you get you case sealing compound off Rex...I use his stuff...very good.

My Bantam video              https://www.youtube.com/watch?v=jjpOFmzRZRI

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Mannanan
Leigh On Sea, Essex. Uk.
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November 1, 2017 - 6:50 pm
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Yes, I guess you mean the Three Bond sealant which is excellent even if it did cost as much as the seals. I made a lovely job of sealing the crankcases back together and thought all was well. Now discovered I can’t get all the gears on the bench so I have to take it apart again. New to Bantam gearboxes and it all looks simple so no idea how I have managed to make a dogs dinner of it. No rush, barrel is in for a rebore (£30) so I have a couple of weeks to play around. Don’t want to leave it until the heart of winter though as it’s perishing cold in that garage.

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nickjaxe
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November 1, 2017 - 8:43 pm
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Sometimes on the bench they dont change as they should....things need to be turning to engage.

I can send you Garys off the forum gearbox assembly guide if you want...I would have been lost without it first time I did it.

But would need your email address to send it to you.

Nick.

My Bantam video              https://www.youtube.com/watch?v=jjpOFmzRZRI

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Mannanan
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November 2, 2017 - 12:10 pm
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Thanks Nick, PM sent.

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Mannanan
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December 6, 2017 - 4:04 pm
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I felt the need to post an update of my (self inflicted) Bantam woes. First, thanks again to Nick for kindly sending me the info for the gearbox rebuild. Beats the Haynes manual by a mile. All done, reassembled but was never happy that I could not select 3rd and 4th on the bench. I convinced myself it would be fine once I got it rolling. Well the engine fires up and the issue with the leaking seals has clearly been sorted so that’s the positive. Now let’s try those gears! Nope, not going well. Only 1st and 2nd can be selected and I know it had four gears before I stripped it. I am pretty sure all gears and selector rollers are fine. I am pretty sure I have made a faux pas with that cam plate and lining up the quadrant. Guess I didn’t quite understand what I was trying to do and I still don’t by looking at the diagram. Guess it will all become clear when I get the enthusiasm to strip it all down and start again. Oh well ....should be a lot quicker on the job next time.

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nickjaxe
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December 6, 2017 - 5:20 pm
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Its very disheartening when you have to strip it again isn't it....been there twice.

I made a stand for my engine...makes it easier to mess about with it on the bench....with a bit of sprocket turning you should be able to get all gears positions...its a fiddle but you can do it.

I'm talking with the engine split laying on its side internals facing up....make sure the selector claw is dropping in all the slots on the quadrant as you try all gears.

I would try that before you take the gearbox apart.

Nick.

My Bantam video              https://www.youtube.com/watch?v=jjpOFmzRZRI

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Mannanan
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December 7, 2017 - 10:02 am
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Yes Nick, I think an engine stand is the way to go. I am used to 70/80’s Japanese two strokes that split horizontally. An absouloute doddle to split and much easier to work on. Definitely won’t be rebuilding until I am sure all those gears are selecting. It may well be sitting in the garage until spring now though.

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