CB250 Engine rebuild

[fastbob]

Is it possible to fit a manual cam chain tensioner ? I fitted one to my ER and it worked wonders. I doubt that anyone makes one but one could be adapted .

Given that it isn't a standard plunger style tensioner I think not, but really why would you bother? The original never gave any trouble, the chain never made any noise and yet it hasn't been stretched to oblivion so I'd say it works absolutely perfectly. Now if a manufacturer can find a way to tension a final drive chain in the same manner and bother to fit hydraulic buckets for automatic valve clearance adjustment then we'll be set!

 

Oh , sorry, I thought you were replacing the cam chain because it had issues . If I'm honest, I fitted a manual tensioner to get an extra 10,000 miles or so out of a cam chain that is close the service limit . The spring in the Kawasaki one just doesn't give you those last two or three clicks .

[fastbob]

Is it possible to fit a manual cam chain tensioner ? I fitted one to my ER and it worked wonders. I doubt that anyone makes one but one could be adapted .

Given that it isn't a standard plunger style tensioner I think not, but really why would you bother? The original never gave any trouble, the chain never made any noise and yet it hasn't been stretched to oblivion so I'd say it works absolutely perfectly. Now if a manufacturer can find a way to tension a final drive chain in the same manner and bother to fit hydraulic buckets for automatic valve clearance adjustment then we'll be set!

Like on a Harley .

[oldgrump]

[mention]Snod Blatter[/mention] and the 1983 CBX750f, that had Hydraulic Valves, a first for Honda. I hated the Rev limiter fitted!!!! Always hitting the dam thing, but never having to do the valve clearances, bliss

[Snod Blatter]

All the more galling that it has been done before and then "forgotten"..

Right, so, a lot of gasket is now scraped off. Time to tackle these oval holes! These are the two at the front, the two at the back aren't anywhere near as bad but the fit is still sloppy around the bolts.

I purchased some steel "bushes" from simplybearings, 12mm outer diameter and 10mm inner diameter - just the job.

They're a lovely tight fit round the new 10mm drill bit, purchased specially for this job along with an 11mm and 12mm.

So, knock it into where the dowel would go (which is 12mm OD) and use it as a guide to drill the holes out in the case.

It sounds so simple, dunnit? Line it up until the bit slides down through the "dowel" without touching the sides and drill it through, then turn it over and use the new 10mm hole to line up the drill, replace the 10mm with 11mm and drill again, then 12mm and drill again. Then insert bush. Bish bosh, steel mounting points at 10mm (which is 2mm larger than what was originally at the front, bonus). But there's a problem with this, I'm not working in an Engineering workshop. What I have is this:

The drill bit can only be moved down by 50mm, this turns out to make it really properly difficult as placing the case on the platform that the drill has makes it too high and the drill bit won't go high enough to go inside the dowel, but if I use the platen at the base then I can't clamp the case down and therefore I can't get it flat enough. This wasn't flat enough at all:

Not even using The Heaviest Weight In The World, a cylinder head from a Mini, was enough to make it flat.

Then it started to rain so I had to chuck everything back in the garage double quick.

So, I need a precision flat piece of metal/wood just thick enough to get the case at just the right height so I can drill it. Turns out that this backyard engineering is a bit tricky.

[Guest Richzx6r]

All the more galling that it has been done before and then "forgotten"..

Right, so, a lot of gasket is now scraped off. Time to tackle these oval holes! These are the two at the front, the two at the back aren't anywhere near as bad but the fit is still sloppy around the bolts.

I purchased some steel "bushes" from simplybearings, 12mm outer diameter and 10mm inner diameter - just the job.

They're a lovely tight fit round the new 10mm drill bit, purchased specially for this job along with an 11mm and 12mm.

So, knock it into where the dowel would go (which is 12mm OD) and use it as a guide to drill the holes out in the case.

It sounds so simple, dunnit? Line it up until the bit slides down through the "dowel" without touching the sides and drill it through, then turn it over and use the new 10mm hole to line up the drill, replace the 10mm with 11mm and drill again, then 12mm and drill again. Then insert bush. Bish bosh, steel mounting points at 10mm (which is 2mm larger than what was originally at the front, bonus). But there's a problem with this, I'm not working in an Engineering workshop. What I have is this:

The drill bit can only be moved down by 50mm, this turns out to make it really properly difficult as placing the case on the platform that the drill has makes it too high and the drill bit won't go high enough to go inside the dowel, but if I use the platen at the base then I can't clamp the case down and therefore I can't get it flat enough. This wasn't flat enough at all:

Not even using The Heaviest Weight In The World, a cylinder head from a Mini, was enough to make it flat.

Then it started to rain so I had to chuck everything back in the garage double quick.

So, I need a precision flat piece of metal/wood just thick enough to get the case at just the right height so I can drill it. Turns out that this backyard engineering is a bit tricky.

 

I'd definitely suggest using a proper engineering company......depending on where in the country you are mate I could help with that obstacle

[fastbob]

I agree . Although I admire your " Can do " attitude you might be best to take it in to an engineering workshop.

[Snod Blatter]

I'd definitely suggest using a proper engineering company......depending on where in the country you are mate I could help with that obstacle

I'm just west of Leicester. Fearing that this indeed may be the way to go (I was umming and ahhing about it right from the start) I tried calling local engineering hero Dave East in Enderby but the number is not recognised, perhaps he has finally retired.

There's also a bloke in Groby who does this kind of thing but last time I used him to get get a seized bolt out it cost me something like £35 so I daren't imagine how much he'd want for this. There's also always a queue to join, no doubt someone will want their Armstrong Siddeley reboring and some pistons made to suit which will take him an age

All I need is a bloke in a shed with a long reach pillar drill..

[smallfrowne]

Use that orange drill on the right.

[Guest Richzx6r]

I'd definitely suggest using a proper engineering company......depending on where in the country you are mate I could help with that obstacle

I'm just west of Leicester. Fearing that this indeed may be the way to go (I was umming and ahhing about it right from the start) I tried calling local engineering hero Dave East in Enderby but the number is not recognised, perhaps he has finally retired.

There's also a bloke in Groby who does this kind of thing but last time I used him to get get a seized bolt out it cost me something like £35 so I daren't imagine how much he'd want for this. There's also always a queue to join, no doubt someone will want their Armstrong Siddeley reboring and some pistons made to suit which will take him an age

All I need is a bloke in a shed with a long reach pillar drill..

 

Do you need this done asap or is there no real time limit on it as I'll be going back down to my parents for a week in late may early June so I could always stop by pick it up and take it to where my dad works and do it for you for a couple of pints

[Bender]

I admire your work but I would have drilled that by hand.

[dynax]

have a look at some metal working forums, you may find a hobbyist local, or see if there is a men's shed local to you,

[smallfrowne]

Have a look at yourself in the mirror and get it drilled be hand.

[julianl]

I'd do it by hand too, if the pillar drill can't reach. If it was a smaller hole I'd suggest using either a pin vice in the drill chuck to extend the reach, or getting a longer drill bit.

Here I am drilling a snapped stud out of an alloy cylinder head (hateful Vauxhall POS).

If you can get a second person to act as a spotter to get a look at the drill from another angle and make sure you're going in straight it can help.

[Snod Blatter]

Do you need this done asap or is there no real time limit on it as I'll be going back down to my parents for a week in late may early June so I could always stop by pick it up and take it to where my dad works and do it for you for a couple of pints

This is a very kind offer, I wanted it to be up and running in May because that is when it turns 25 but there's no other reason for it. In the meantime the Kawasaki is doing okay at the small bike duties (commuting, general knobbing about) so I'm not too fussed. I may take you up on this if I can't find anything else.

 

have a look at some metal working forums, you may find a hobbyist local, or see if there is a men's shed local to you,

This is a great idea, I'll have a look!

 

I admire your work but I would have drilled that by hand.

But you're a bending unit not a drilling unit??

There's no way I can do this "freehand", the holes have to be in the same place in each case or the bolts won't go all the way through. That's why I was using the dowel as a guide but it turns out I just don't have the kit. This is a bit of actual engineering, not just drilling a hole so something will go through it

[Bender]

Yes I understand that but I'm still sticking with drilling by hand, I have done similar on casings in the past and made inserts to fit and never been so far out that they didn't.

End of the day it's yours and I appreciate your not happy doing it like that.

[Guest Richzx6r]

Do you need this done asap or is there no real time limit on it as I'll be going back down to my parents for a week in late may early June so I could always stop by pick it up and take it to where my dad works and do it for you for a couple of pints

This is a very kind offer, I wanted it to be up and running in May because that is when it turns 25 but there's no other reason for it. In the meantime the Kawasaki is doing okay at the small bike duties (commuting, general knobbing about) so I'm not too fussed. I may take you up on this if I can't find anything else.

 

have a look at some metal working forums, you may find a hobbyist local, or see if there is a men's shed local to you,

This is a great idea, I'll have a look!

 

I admire your work but I would have drilled that by hand.

But you're a bending unit not a drilling unit??

There's no way I can do this "freehand", the holes have to be in the same place in each case or the bolts won't go all the way through. That's why I was using the dowel as a guide but it turns out I just don't have the kit. This is a bit of actual engineering, not just drilling a hole so something will go through it

 

Well if you need me to sort it for you I'm sure I can pull a few strings