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Detent plunger function?


gasgasshetland
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Hi there, I’m just setting about a restoration of a Sherpa 250 198A. I’ve drained the oils which were not in a good way. But I went to turn the engine over and it seemed as though it was jammed. Lots of head scratching, and eventually left it and went back into the house. Was speaking with my wife and she said what had I done exactly and was there anything that was not in place. My thoughts are that the detent plunger bolt is removed.

Will that stop the engine from turning over. 

Thanks in advance 

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The detent plunger holds the selected gear in place, this component can sometimes make gear selection feel very stiff. With the detent removed you could possibly have selected one gear and caught another which would lock the gearbox. I am assume here that the piston in the cylinder is free and not seized. Alternatively you could try a role reversal and let your wife with her logical thinking take over the restoration. This would leave you to do the cooking, dusting and hoovering, but you would be able to use your 4rt for the shopping??

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  • Haha 3
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Haha. Yeh might be better to get her to have a crack at it.  The barrel is off the bike. I bought the bike a couple of months ago. And am sure it was turning over when I got it as a mate picked it up for me so it was unseen. Though my brother in law who had told me about it said it was supposed to have been a runner. 

I did try selecting neutral while it was removed and as you say I might have locked it up. Bugger.  

Will have look at it tomorrow 

Will I need to split it to get it unlocked. 

 

Cheers 

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If the rest of the gearbox is working properly, removing the detent plunger will not cause or allow it to go in more that one gear at a time. Taking the detent plunger out will mean that you might have trouble getting the shift mechanism to work normally. There are many other possibilities for why the crankshaft won't rotate though. A good way to work out why the crankshaft won't rotate is to take the engine covers off. That way you will know if it is one of the many causes external to the gearbox that is causing the problem

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your better off just striping it there easy to work on done loads over the years the gear drum has what i describe has a flower where the plunger goes neutral is the bigger groove on the flower. make sure all gears are working before putting the other half off the crank case on and there's a small spacer that a lot lose that goes on the end off the kick start shaft.

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Thanks Bondy,  yeh it’s going to be stripped down. The detent plunger is quite worn looking so will replace it while am at it. It’s turning over freely now but I’d say the bearings sound a little rough. It’s getting a pretty much full rework of the bike as I bought it unseen but complete and it’s needing a reasonable bit of work doing to it all. I had a 199A a few years ago that I restored, but it was almost too nice to ride, it was sold to a collector p, but this one is going to be ridden for sure  hopefully have it done for the new 2 day in September in Kinlochleven  if I can get an entry  

cheers

 

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