Basket Cases

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Greg Harding
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Re: Basket Cases

Postby Greg Harding » Mon Mar 27, 2017 10:08 pm

Hi Everyone,

TriCub wrote: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.

George, thanks for the explanation as this is something I have not done before, there is a wealth of local knowledge. My machinist friend heated the cylinders before pressing the sleeves out, a job he has done plenty of times and if you look closely you can see where the sleeve scraped it's way out. Another Mate is the Motorcycle Mechanic and has been advising me as well re what will and won't work.
JC1 wrote: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.


John, the port heights diagram were approximations of the cylinders without the Sleeves! Below is another drawing I have done with approximate measurements of liners but have not measured to inlet tract yet. Well spotted with regards to side port instead of Centre port and I think bringing the twin downtubes together will make it a bandaid modification so I am thinking a bigger round downtube. There is quite a bit of room to play with as the standard exhaust is in front of the downtubes and I will have a header pipe similar to or same as 247.
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Here is a photo looking in the inlets, luckily :montesa have provided me with a bolt up manifold so I can reduce the passage to fine tune for low speed without removing the cylinder. The spigot needs to be reworked to suit 26 mm carby and may be elevated to clear the clutch cable?
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Yes there is a fair bit to consider, some of it way over my head but I think I am heading in the right direction. Imagine 247 reliability with 242 Handling!
David, just thinking about your :yamaha Alpina magneto cover, maybe make an adaptor plate and cut down a TY cover something like what :Honda: have done with TLM 220/260 to fit a bigger weight onto a trail bike Magneto?
1490574687945.jpg
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The closest thing to a TLM is the MTX 200, some parts interchange:
1490574562547.jpg
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Re: Basket Cases

Postby David Lahey » Mon Mar 27, 2017 10:38 pm

Greg Harding wrote:David, just thinking about your :yamaha Alpina magneto cover, maybe make an adaptor plate and cut down a TY cover something like what :Honda: have done with TLM 220/260 to fit a bigger weight onto a trail bike Magneto?
1490574687945.jpg

The closest thing to a TLM is the MTX 200, some parts interchange:
1490574562547.jpg

That's a good idea Greg. Thankyou. I think it would even be possible to use a DT cover if I make a spacer about 6mm to 8mm thick


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Re: Basket Cases

Postby David Lahey » Mon Mar 27, 2017 10:45 pm

David Lahey wrote:
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

Here are two 5 speed round barrel cylinders. You can see the difference in the shape of the casting at the exhaust attachment that Brownie was talking about and I've put in a photo from the top to show the (lack of) stampings on one of them
Attachments
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IMAG4580.jpg
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Re: Basket Cases

Postby David Lahey » Mon Mar 27, 2017 10:51 pm

Greg Harding wrote:The closest thing to a TLM is the MTX 200, some parts interchange:
yamaha-dt200r-1.jpg
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I just realised how much that Honda Japanese-market trailbike looks like a Yamaha DT200R (1988 to 1996)


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Re: Basket Cases

Postby brownie » Tue Mar 28, 2017 12:51 pm

David that unstamped ones exhaust outlet seems to be angled downwards more may be just the photo though
All the 5 speed round barrel ones I've looked at are the same design as your 27 stamped one. From about m80 on the exhaust outlets outer diameter is larger. Actually any of the upswept pipe round barrel 5 speed Bultacos I've looked at seem to have a similar designed exhaust outlet as your 27 stamped one



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Re: Basket Cases

Postby JC1 » Tue Mar 28, 2017 1:13 pm

Greg Harding wrote:John, the port heights diagram were approximations of the cylinders without the Sleeves! Below is another drawing I have done with approximate measurements of liners but have not measured to inlet tract yet. Well spotted with regards to side port instead of Centre port and I think bringing the twin downtubes together will make it a bandaid modification so I am thinking a bigger round downtube.


Greg, on those dimensions it works out the same - the transfer ducts in the 44M cyl will have to be raised about 2mm to match the Cota liner.

It would be interesting to compare the 242 port heights & widths to that of the 247. I suspect the 242 transfers maybe close to the width of the ducts in the 44M cylinder. The 242 was said to have very nice power - strong & broad - so it maybe fairly easy to upgrade your combination cylinder to 242 specs and have an even nicer bike.


The Villiers-engined Sprite trials bikes had close-spaced parallel double downtubes with a side port cylinder. Didn't look too bandaid.



David Lahey wrote: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.


David, that is a strange combination. Some weird ones came out of the factory. They seem to have often just grabbed the first thing that came to hand, if it fit.

Its not unusual for the cyl not to be stamped. About half my round Bul cylinders are unstamped. That one may be from a Metralla (M23) .


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Re: Basket Cases 3 head Madness

Postby Greg Harding » Wed Mar 29, 2017 9:57 pm

Hi Everyone,
JC1 wrote:Greg, on those dimensions it works out the same - the transfer ducts in the 44M cyl will have to be raised about 2mm to match the Cota liner.
It would be interesting to compare the 242 port heights & widths to that of the 247. I suspect the 242 transfers maybe close to the width of the ducts in the 44M cylinder. The 242 was said to have very nice power - strong & broad - so it maybe fairly easy to upgrade your combination cylinder to 242 specs and have an even nicer bike.

John, I really like how you think so I have added some more measurements of 3 sleeves from the inside as 242 is a chrome bore:

The 242 cylinder and piston are serviceable, it was a broken kickstart that stopped this Bike! I have only ever ridden one :montesa 242 that belonged to Chippy and yes I was very impressed with how it rode and the power delivery however I was really nervous about stalling it after Chippy handed it to me with the motor running as it was long overdue for the kickstart to snap off or strip the drive Gears!
Greg Harding wrote: :montesa knew this was the era to change the shape of your head:

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242--------------------------------------------------------------------------------------44M----------------------------------------------------------------------------------------------247
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44M
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247
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242
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As you can hopefully see, the 242 is quite a bit different to the other 2 especially in the inlet area. Just don't ask me to explain how it works! I think the bridge in the exhaust port is a better idea for longevity and yes John the 242 transfer duct at the base of the cylinder is close to 247. If anyone can Come up with a better idea than 2 mm of the top and 5 mm off the bottom, please feel free to let us know as it is all hypothetical at this Stage? The 242 has more bore above the exhaust port makes me think it would have a higher compression Ratio?

Thank you Everyone for your Input!


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Re: Basket Cases

Postby JC1 » Thu Mar 30, 2017 7:03 pm

Greg, I think there's a few dimensions on your 'mudmap' mixed up there.

However with the lower but wider transfers on the 242 and an extra boost port, it looks like the total overall tranfer/boost area is a little more on the 242 than on the 247.

But with such vastly different porting arrangements the idea of matching the 247 liner to 242 specs would be more than a little impractical.

Its looks to me like it maybe a whole lot less work just to get a new kickstarter gear made up for the 242 engine out of high strength steel & properly heat treated, then use the 242 engine in the 242 roller.

As a matter of interest how does a 242's power compare to a KT's?
(cos those 242 porting specs look remarkably similar to a KTs)


But assuming you still want to consider using the 247 liner in the 44M cylinder it would be interesting to compare the width of the inlet bridges on the liners as the 44M looks considerably wider which may give some grief.


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Re: Basket Cases

Postby TriCub » Fri Mar 31, 2017 11:21 am

As John has pointed out the bridge width on the intake could be an issue. If the crinkle rear transfer passage is wider than intake bridge you would need to weld the alloy passage in the barrel and bring it's width down before it is bored out to take the bigger sleeve. All possible but not economical.
The other idea would be to put the sleeves back where they came from and fit a longer stroke crank to match the barrel.



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Re: Basket Cases Montesa Madness

Postby Greg Harding » Sat Apr 01, 2017 7:44 am

Hi Everyone,
JC1 wrote:Greg, I think there's a few dimensions on your 'mudmap' mixed up there.

John, perhaps I should explain that I snap the photos at lunch time and measure things and post after hours. The mud map dimensions can only be approximate as the ports are generally angled and around the curve of the sleeve. I have checked the dimensions and the only mistake I found was in my quote about the width of the transfer duct at the base of the cylinder should have read the the 242 is close to the 44M not 247.
242 = 30 mm wide, 44M is 29 mm wide and 247 is 25 mm wide.
As for comparing 242 to KT, it is too long ago to be accurate but similar power only :montesa lacked that beautiful :kawasaki whine from the straight cut gears.
Here is another mud map of 44M and 247 inlet ports:
EDIT, enough light for photo now:
1490994512391.jpg
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TriCub wrote:As John has pointed out the bridge width on the intake could be an issue. If the crinkle rear transfer passage is wider than intake bridge you would need to weld the alloy passage in the barrel and bring it's width down before it is bored out to take the bigger sleeve. All possible but not economical.
The other idea would be to put the sleeves back where they came from and fit a longer stroke crank to match the barrel.

George, yes I see what you are saying, John mentioned quick metal before and I have no experience using it but would it be possible to adjust the duct width instead of Welding?
Secondly, 247 has a shorter stroke for a reason, I was thinking it must be better for Trials with motors running at lower Revs?
JC1 wrote:Its looks to me like it maybe a whole lot less work just to get a new kickstarter gear made up for the 242 engine out of high strength steel & properly heat treated, then use the 242 engine in the 242 roller.

MMM, I see what you are saying here, how often do you see a 242 Competing? We have discussed this before, the :montesa 242 bottom end us fundamentally a 123 which on paper sounds like a good idea: small , compact and Light! In reality however, :montesa tried to squeeze too much into too small an area, yes parts got bigger through the series as capacities grew to 238 cc as is the case with 242. Here is a photo of where I think the problem lies:
1490989879405.jpg
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That little hole that my pinky is pointing at is where the missing kickstart shaft used to live. The :yamaha kickstart shaft in the photo is too big to fit as both gear and assembly are too big! Now I think you are wondering what bike the :yamaha one came out of, it is a 72 cc TY 80. To quote 4 Non Blondes with different shaped heads: BIGGER, BETTER, FASTER, MORE :!:
1490989932538.jpg
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