Basket Cases

Need help finding information or parts for that old machine in your shed? Someone in here will know!

Moderator: Moderators

David Lahey
Champion
Champion
Posts: 4062
Joined: Thu Jun 05, 2003 7:01 pm
Bike: Many Twinshocks
Club: CQTC Inc, RTC Inc
Location: Gladstone, Queensland

Re: Basket Cases

Postby David Lahey » Sun Mar 26, 2017 10:20 am

Greg I wouldn't be too worried about the sleeve holes not lining up exactly with the cast ports on the 247. I was horrified the first time I saw how poorly the sleeve port holes lined up in my early :Bultaco: Matador and M49 barrels, but the M49 motor runs incredibly well with some of the sleeve ports more than 2mm smaller than the ports in the casting, and I think my :ossa MAR cylinder is similar, and it also runs extremely well.
I'm thinking that it would be important on a racing motor to reduce turbulence/drag but may actually be a benefit in a trials motor for low RPM operation.
Seeing your porting story again has reminded me to post up a photo on a similar topic - later today


relax, nothing is under control

TriCub
Expert participant
Expert participant
Posts: 273
Joined: Fri May 28, 2010 11:38 am
Bike: Triumph
Club: Wester districs trials club

Re: Basket Cases

Postby TriCub » Sun Mar 26, 2017 2:52 pm

Maintaining the shape of the top part of the transfer ports is the most critical so taking 2 mm from the top and 5mm for the bottom should work ok. That gives only a little bit of barrel to remove to get the match at the transfer top. Be careful after the sleeves goes into the barrel(don't press it in) as it will probably not be round anymore.

I should clarify the bit about not pressing in. Sleeve has to be a press fit but if you press it in there is a chance that a sharp port edge will tear away part of the cylinder on the way in. You have to heat the cylinder then drop in the sleeve giving you about 2 seconds to line up the ports.



David Lahey
Champion
Champion
Posts: 4062
Joined: Thu Jun 05, 2003 7:01 pm
Bike: Many Twinshocks
Club: CQTC Inc, RTC Inc
Location: Gladstone, Queensland

Re: Basket Cases

Postby David Lahey » Sun Mar 26, 2017 5:50 pm

While on the topic of matching or not matching ports in liners to the casting here is a :Bultaco: M85 Alpina cylinder in which someone has trimmed the liner port out to match the cast port, but only on one side of the exhaust port. The photos show the bridged exhaust port from the inside and the outside. In this case the standard side of the exhaust port has a step down of about 3mm from the cast section to the liner, so the side that has been fiddled with has the top edge of the exhaust port 3mm higher than it should be.
Yes that liner is fairly useless.
There are more stories about that M85 basket case yet to come
Attachments
IMAG4559.jpg
IMAG4559.jpg (980.07 KiB) Viewed 6050 times
IMAG4563.jpg
IMAG4563.jpg (627.04 KiB) Viewed 6050 times


relax, nothing is under control

JC1
Expert participant
Expert participant
Posts: 387
Joined: Tue Apr 26, 2011 4:15 pm
Bike: Bul, KT, TY
Club: wdtc
Location: Toowoomba, Qld

Re: Basket Cases

Postby JC1 » Sun Mar 26, 2017 6:23 pm

Greg, you've got a very fertile mind. Must have too much time on your hands.

Love the "what if..." thinking tho. Kindred spirits!

As you'd know the 44M has diff bore & stroke (70x64) to the 21M Cota (72.5x60) .

The 44M was said to have the same cylinder/liner as the Cappra VR motocrosser (73M) which was a rocket - hence the larger ports - and the 44M/73M engine as a whole is quite different to the 247 Cota in numerous ways.

I used to have parts manual for the 44M but don't any more so I can't check numbers specific to the 44M. But according to the parts manuals I do have, the 21M rod is a 73 part # which means its common to the 73M cappra & I presume to the 44M.

With the same rod but 4mm longer stroke, you'd expect the 44M cylinder to be 2mm taller than the Cota 21M, if the piston heights (relative to the gudgeon) were the same. I know the 73M used a very tall piston (I used to have one), and since your 44M cylinder is 7mm taller I'm guessing that the 44m piston is 5mm taller (gudgeon to top edge of piston) than the 247 Cota.

Which means, if that is the case, that 2mm off the top of the 44M cylinder & 5mm off the bottom, as you suggested, should be correct for using the Cota liner & piston. If I've understood you correctly, and the ports in the liner can be made reasonably close to those in the cylinder it should work.


With a 5mm longer piston & 4mm longer stroke, that means the inlet port sits a fair bit lower in the 44M cylinder/liner than in the Cota liner and you can see that in your pics of the liners side by side. So that inlet area might require considerable adjustment to suit the Cota liner. And you may need to fill in the 44M inlet tract with some Devcon/JBweld to reduce its cross-sectional area so as to maintain decent mixture velocity at low rpm, since it was sized to suit a much larger carb than the Cota. (I'd think it would be better to do that before you bored out the cylinder to take the Cota liner.)

I'd be tempted to widen the transfers a little in the Cota liner while you're at it.

PS How accurate are those port heights that you posted? They are quite diff to what I've measured for both 247 Cota & VR Cappra (measured down the bore).


"Men are never more likely to settle a matter rightly than when they can discuss it freely"

JC1
Expert participant
Expert participant
Posts: 387
Joined: Tue Apr 26, 2011 4:15 pm
Bike: Bul, KT, TY
Club: wdtc
Location: Toowoomba, Qld

Re: Basket Cases

Postby JC1 » Mon Mar 27, 2017 2:17 pm

Greg, you got me thinking it thro to see what's involved in matching it all up, so for what its worth here's a few more tho'ts:
(I can't do much else at the moment)

Looks like the boost port area may need a fair bit of attention too. It appears to be a fair bit wider in the 44M liner & cylinder, as is the inlet tract where it splays around that boost port tract, which may mean that you'll need to 'fill in' the boost port tract a little in the 44M cylinder. Otherwise the inner edges of the Cota liner's inlet port may open into the boost port tract of the 44M cylinder (if that makes sense)


As for port heights, if my maths are correct and going by the dimensions I have for VR Cappra & 247 Cota port heights, if you take the 2mm off the top of the 44M cylinder (& 5mm off the bottom) to suit the Cota liner/engine, the exhaust port should take care of itself (tho it'll be considerably larger all round in the 44M cylinder than in the Cota liner - not necessarily a good thing, but it should still work).

Then it looks like the top of the transfer & boost port ducts in the 44M cylinder will have to be raised about 2mm & the top of the splayed inlet ducts in the cylinder will have to be raised about 3mm, to suit the Cota liner. The bottom of the inlet ducts in the 44M cylinder will be about 6mm lower than in the Cota liner which I'd think should be filled as per the post above.

Those are ball-park figures assuming the 44M cylinder is the same as the VR, and that the angle of the tops of the ports in the liners (VR/44M & Cota) are the same.

Seems to me that's quite do-able for a man of your skills - even if a lot of work.

But I'm wondering how you're going to fit a side-port barrel into a double downtube 242 frame. Convert it to single downtube? Or pull the downtubes in close to each other?
No doubt you'll already have a solution in mind.



Dave, what do you reckon they opened up one side of that port by working thro the exhaust outlet, then realized it was going to be much harder to do the other side the same way so just gave up!?

Seems to me that's a sherpa liner in a matador barrel on the alpina


"Men are never more likely to settle a matter rightly than when they can discuss it freely"

David Lahey
Champion
Champion
Posts: 4062
Joined: Thu Jun 05, 2003 7:01 pm
Bike: Many Twinshocks
Club: CQTC Inc, RTC Inc
Location: Gladstone, Queensland

Re: Basket Cases

Postby David Lahey » Mon Mar 27, 2017 5:06 pm

JC1 wrote:Dave, what do you reckon they opened up one side of that port by working thro the exhaust outlet, then realized it was going to be much harder to do the other side the same way so just gave up!?

Seems to me that's a sherpa liner in a matador barrel on the alpina


I'll have another look and see if that explanation about modifying half the exhaust port looks likely John

The factory stamping on that cylinder in the photos is 27, which is the same number as on my current M49 cylinder and also on the barrel that came on my M49 which I assumed was from either an M27 or a Matador or an M49.
I think the cylinder on the M80 I got from you has a different stamping, and I think I read somewhere that the M27 and early M49 shared a cylinder design with the round-barrel Matador, and then the Sherpa T design deviated from Matador design around the time of the late model M49 and M80?
Are you thinking that it is Matador because of the 3mm step down to the liner exhaust port?


relax, nothing is under control

JC1
Expert participant
Expert participant
Posts: 387
Joined: Tue Apr 26, 2011 4:15 pm
Bike: Bul, KT, TY
Club: wdtc
Location: Toowoomba, Qld

Re: Basket Cases

Postby JC1 » Mon Mar 27, 2017 7:55 pm

David Lahey wrote:Are you thinking that it is Matador because of the 3mm step down to the liner exhaust port?


Yes David that was my thinking. Fair chance they would have used the matador cylinder for the sherpa in those days, as you indicated, and stamped it 27 cos of the different liner used for the sherpas. As I recall the transfer & inlet ports are quite similar on the matadors & sherpas of that era.

As I understand it the M27 cylinder/liner combination was used on all 250 sherpas from M27 to M124. Sounds like it was used on the corresponding 250 Alpinas too.


"Men are never more likely to settle a matter rightly than when they can discuss it freely"

David Lahey
Champion
Champion
Posts: 4062
Joined: Thu Jun 05, 2003 7:01 pm
Bike: Many Twinshocks
Club: CQTC Inc, RTC Inc
Location: Gladstone, Queensland

Re: Basket Cases

Postby David Lahey » Mon Mar 27, 2017 8:49 pm

JC1 wrote:Dave, what do you reckon they opened up one side of that port by working thro the exhaust outlet, then realized it was going to be much harder to do the other side the same way so just gave up!?

Yes I had a good look tonight and can see the exhaust port work was done with a file, and there is a carbon layer over the file marks so it was run like that. If they had a porting tool available they probably would have done both sides.
I do have another mystery though because the cylinder that came on my M49 has no ID stamping, and has an larger inlet tract designed for a larger carby than the Sherpa T and Alpina. I had assumed that this was a Matador cylinder because of these two things, but the top of the exhaust port hole in the liner is flush with the casting and measures the same distance from the top of the liner as the (unmodified) exhaust port hole in the liner in the cylinder that came on the M85.
I should do measurements of all the ports in both cylinders


relax, nothing is under control

brownie
TA Supporter
TA Supporter
Posts: 152
Joined: Wed Jan 14, 2009 10:46 pm
Bike: Bultaco's
Club: denman
Location: armidale. nsw

Re: Basket Cases

Postby brownie » Mon Mar 27, 2017 9:33 pm

Here's a link for a m26 cylinder on eBay and it has 26 stamped on it
http://www.ebay.com/itm/BULTACO-MATADOR ... 7675.l2557
The m75/82 has a 75 part number going by my parts book so matador cylinders must be different in some way.
As JC1 says all the round barrel 5speed Sherpas have the same liner 27.10-028 part no. the m150 as well. The m85 Alpina has the same liner too.
The actual cylinders are all the same part no. 27.10-026 from m27 to m150 and the m85 although there is 3 modifications as far I can tell that was around mid m49,m80 and the last at m150 the only difference I can see is where the exhaust flange screws in,the alloy is thicker about 2mm thicker comparing my m49 to my m124



David Lahey
Champion
Champion
Posts: 4062
Joined: Thu Jun 05, 2003 7:01 pm
Bike: Many Twinshocks
Club: CQTC Inc, RTC Inc
Location: Gladstone, Queensland

Re: Basket Cases

Postby David Lahey » Mon Mar 27, 2017 10:00 pm

brownie wrote:Here's a link for a m26 cylinder on eBay and it has 26 stamped on it
http://www.ebay.com/itm/BULTACO-MATADOR ... 7675.l2557
The m75/82 has a 75 part number going by my parts book so matador cylinders must be different in some way.
As JC1 says all the round barrel 5speed Sherpas have the same liner 27.10-028 part no. the m150 as well. The m85 Alpina has the same liner too.
The actual cylinders are all the same part no. 27.10-026 from m27 to m150 and the m85 although there is 3 modifications as far I can tell that was around mid m49,m80 and the last at m150 the only difference I can see is where the exhaust flange screws in,the alloy is thicker about 2mm thicker comparing my m49 to my m124

Thanks Brownie I had noticed the different thickness castings around the exhaust attachment and wondered what was happening there. The thicker one can be a pain to work on the front engine mounting bolt.
Now I'm wondering why one of my round barrel 5 speed Sherpa T/Alpina cylinders (the one that has the bigger inlet tract) has no ID stamping on it. I'll take a photo of it and post it up


relax, nothing is under control


Return to “Twinshock & Classic Trials”

Who is online

Users browsing this forum: No registered users and 30 guests