Honda-SOHC
SOHC.co.uk Forums => Other Bikes => Topic started by: AndyD on September 03, 2024, 08:07:55 PM
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Hi,
Hoping maybe someone can help with a query on my 1980 Yamaha XT250.
Had problems with the decompression mechanism and I think it's down to the kickstarter assembly and the relative position of the 'lug' on the starter assembly.
Hoping someone may have a photo or knowledge of where the lug on the assembly should be positioned - I think the existing as shown in the photo is incorrect but can't find any reference to correct assembly in manuals or online.
Position is adjustable b taking apart the assembly so I'm guessing it's been put together wrong in the past (the engine had signs of many bodges and damage so no surprise!).
Hope that makes some kind of sense!
[attach=1]
Cheers,
Andy
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Yamaha were pretty good in marking parts that could be fitted wrong, look for a dot
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How are the kickstart and decompression systems linked?
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There is an external cable
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Thanks guys,
You’re right Bryan, Yamaha seem to use dots for alignment throughout the engine which is quite neat, however on the kickstart assembly I couldn’t see any matching mark for the two parts of this.
Hopefully the photos shows the assembly clearly – the front ‘lug’ position is what I’m trying to clarify as it sets where the decompressor activator sits. This is a pivoting part that uses a cable to hold the exhaust valve open during starting. The rear lug locates into a holder in the crankcase so moving the relative positions front and back is what sets the position for the decompressor action.
[attach=1][attach=2][attach=3]
The gear spins on the spindle with the front and back parts able to be positioned by moving positions on the splined shaft. There is a clear dot on the front lug but I can’t find anything on the rear part of decompressor spindle / crankcase etc. etc.
I can’t find anything in the Yamaha or Clymer manual about the setting and the photos are not very clear so I’m a bit wary of basing it on these.
I hoped to find a photo of this somewhere on Google but have failed so far.
The engine has had a tough life and been subject to many (poor) repairs and ‘alternative’ assembly methods so it’s likely the kickstart / decompressor has been put together wrong in the past.
If I can’t find anything conclusive I guess I’ll have to try different configurations to see what could work but I don’t want to keep taking the circlip off the assembly in case it starts getting looser etc.
Cheers,
Andy
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Apologies for the repeated image - had problems with site crashing half way through typing and seem to have clicked a few extra buttons somewhere!
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I dont know if there's anything in this link that could help.
https://www.ebay.co.uk/itm/362506112599
Shows parts schematic,, claims component for xt250 etc.
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We have/had a member here who is a Yamaha enthusiast - he made some parts for them on a 3D printer for clock mounts.
His user name was allankelly1 might be worth a PM to him.
He sold his 400 so not very active here now.
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That dot will line up with something, suprises me if not mentioned in genuine Yamaha manual, not surprised not mentioned in haynes or clymer(same firm now)
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Thanks,
Had another really close look (even put the reading glasses on) but couldn't see any matching dot.
I've had a good play with it and set it where I think it 'feels' right in terms of operating the decompressor mechanism - it's one of those assemblies where it's really not obvious how it all works but slowly becomes clearer after a good study and multiple trial assemblies.
With the cover back on it now at least does something that looks 'right' when the kickstarter is pushed so hopefully once I get a couple of other bits done I'll get a chance to see if it works as designed.
It's a nice, relatively simple bike to work on generally - although as with seemingly all old bikes getting the carb on or off is a royal pain and that's next on the list!
Cheers,
Andy