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Bultaco Sherpa t350


MarkB2001
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Hello, I started the project of rebuilding my my 1973 Sherpa. I’m quite young, without much previous knowledge. Regrettably. I’ve got the bike all apart. I’ve had the frame powder coated etc. However after taking the engine completely apart. With my lack of experience. I’m beginning to struggle and get overwhelmed. My hopes is to learn from this project and gain skills from it. So I don’t want to give up on what I’ve started. I’ve been using a few different manuals such as the Haynes one. I’ve bought some parts to replace, such as new gaskets, electronic ignition, clutch plates etc. However I don’t really know the key parts that should get replaced in a rebuild. The gears are my main concern, I don’t know if they’re worn or anything from looking at them. They’re so many parts to the gears, which panic me to go wrong with. So what I’m asking for is advice really, or perhaps someone willing to allow me to massage regularly on a private basis, so I can ask (many) questions. On the rebuild and parts etc. 
 

any help would be massively appreciated.

thanks,

Mark. 

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19 minutes ago, motovita said:

 When inspecting gears focus on the dogs on the sides of the gear and the surfaces they engage on adjacent gears.

Okay great Thankyou, will it be obvious to see if they’re worn ?

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3 hours ago, MarkB2001 said:

Okay great Thankyou, will it be obvious to see if they’re worn ?

Yes, wear will be fairly evident- if there are obvious burrs on the edges you can clean them up with a fine file. Look at the dogs as well as the edges of the gear teeth themselves. The kickstart ratchet can be quite worn and hooked and may need to be replaced if it is too far gone. Also check for burrs on the selector drum, and the clutch basket too, all these parts need to be able to slide and engage smoothly with one another. Looks like a nice job so far. Is that one of those Indian repro tank units, or did you strip and polish the original? All we see are fibreglass ones over here.

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Inspect the gearbox output shaft. It is a short shaft that will have either a pair of sintered bronze bushes or a pair of needle roller bearings inside where it runs on the main gearbox shaft. Both types can wear/fail and cause consequential damage to the gearbox gears due to misalignment (breaks teeth off). Wear in the sintered bush type is very common. Both the shaft surface and the bushes might be worn. I haven't seen a needle roller type fail but it would probably be more spectacular.

Check that the kickstart return stop is not bent or burred and has a nice action. This is a fairly common failure point.

Also there is supposed to be an aluminium washer on the end of the kickstart shaft. This may be worn out or missing.

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14 hours ago, Bloomfield said:

  Is that one of those Indian repro tank units, or did you strip and polish the original? All we see are fibreglass ones over here.

Homerlite alloy tank/seat unit, standard on models 124/5 and 150/1, etc. supplied in UK. (see front cover of Heinous manual).

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Mark -

Based on my experience with these engines, your main area of concern is likely to be the crankshaft assembly and its bearings and seals, and piston and bore, rather than problems with the gearbox. These tend to be reasonably robust, although possible weaknesses are covered in feetupfun's post.

Did you use heat when dismantling ?  Difficult to see, but from your tenth picture it looks like main bearings are possibly loose on shafts........

Are you in the UK ?

Don't worry about being quite young and lacking experience - we all were once !

Edited by lorenzo
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15 hours ago, Bloomfield said:

Yes, wear will be fairly evident- if there are obvious burrs on the edges you can clean them up with a fine file. Look at the dogs as well as the edges of the gear teeth themselves. The kickstart ratchet can be quite worn and hooked and may need to be replaced if it is too far gone. Also check for burrs on the selector drum, and the clutch basket too, all these parts need to be able to slide and engage smoothly with one another. Looks like a nice job so far. Is that one of those Indian repro tank units, or did you strip and polish the original? All we see are fibreglass ones over here.

Great Thankyou, yeah like Lorenzo said it’s a homer lite tank, made in Solihull Birmingham. I don’t know a huge amount about them but I really like how it looks.

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43 minutes ago, lorenzo said:

Mark -

Based on my experience with these engines, your main area of concern is likely to be the crankshaft assembly and its bearings and seals, and piston and bore, rather than problems with the gearbox. These tend to be reasonably robust, although possible weaknesses are covered in feetupfun's post.

Did you use heat when dismantling ?  Difficult to see, but from your tenth picture it looks like main bearings are possibly loose on shafts........

Are you in the UK ?

Don't worry about being quite young and lacking experience - we all were once !

Thankyou, I look at these parts aswell, yes I heated it when dismantling. Yes I’m in the UK

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9 hours ago, feetupfun said:

Inspect the gearbox output shaft. It is a short shaft that will have either a pair of sintered bronze bushes or a pair of needle roller bearings inside where it runs on the main gearbox shaft. Both types can wear/fail and cause consequential damage to the gearbox gears due to misalignment (breaks teeth off). Wear in the sintered bush type is very common. Both the shaft surface and the bushes might be worn. I haven't seen a needle roller type fail but it would probably be more spectacular.

Check that the kickstart return stop is not bent or burred and has a nice action. This is a fairly common failure point.

Also there is supposed to be an aluminium washer on the end of the kickstart shaft. This may be worn out or missing.

Do you have any information or now where I can look to make sure they’re all aligned correct ? 

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