Matching Cases?

MxSkillz
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MxSkillz
Edited Date/Time 1/22/2019 5:31pm
Hey guys.. i was just wondering if anybody with any bike that has a few mods done has had their cases matched with their cylinder and gasket as part of their mods?.. Do you think this mod helped with the performace of the motor? Is it worth it to do? Did you feel a difference and can you explain how?

I see almost all engine tuners offer this service and was just wondering what it does to help? To me it sounds like its helps with having no restrictions for fuel flow.. which in turn will help performance.. just wondering and want to hear from people who have done this.. thanks
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newmann
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newmann 12/13/2011 7:58pm
12/13/2011 7:58pm
My 74 CR250 vintage racer has everything from the custom aluminum air box with machined inlet, carb, intake manifold (piston port/no reed valve),cylinder, cases and exhaust manifold all matched up. Runs better than any 74 CR250 ought to.
MxSkillz
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MxSkillz 12/13/2011 8:01pm
12/13/2011 8:01pm
sweet.. has anyone else dlone this?
Tim507
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Tim507 12/13/2011 8:56pm
12/13/2011 8:56pm
Matches the case's should include surfacing and the centerline of shafts. XY axis measurements, that is a blue printed caseSmile

This is the foundation of an excellent motor.
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MxSkillz
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MxSkillz 12/13/2011 9:04pm
12/13/2011 9:04pm
Thanks alot for the replies guys.. So it definitly sounds like this will be good mod.. I dont want to do too much.. but basically make the best out of the motor.. anybody else has had this done.. im just trying to understand how this will help? thanks

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motokiwi
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motokiwi 12/14/2011 2:13am
12/14/2011 2:13am Edited Date/Time 12/14/2011 2:14am
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Fleece192
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Fleece192 12/14/2011 3:40am
12/14/2011 3:40am
I had this done for a yz125 years ago. The engine builder, Mr Marsh. Matched the cylinder with the bottom end, opened up the ports and made them look like glass. Relived the exhaust port and put a window in the piston. It was the fastest 125 we ever had. Ever. O yea also squished the head.
E-man811
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E-man811 12/14/2011 5:34am
12/14/2011 5:34am
Fleece192 wrote:
I had this done for a yz125 years ago. The engine builder, Mr Marsh. Matched the cylinder with the bottom end, opened up the ports and...
I had this done for a yz125 years ago. The engine builder, Mr Marsh. Matched the cylinder with the bottom end, opened up the ports and made them look like glass. Relived the exhaust port and put a window in the piston. It was the fastest 125 we ever had. Ever. O yea also squished the head.
Ditto That.

My Mr. Marsh Sr. built 1993 Cr125 is the fastest 125 I've ridden to this day.

Yes, matching the cases and gasket to cylinder is worth it.
ama530
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ama530 1/22/2019 12:44pm
1/22/2019 12:44pm
Yes, it is worth doing. I learned how to port and polish from the late John Carr. He did allot of the work for Eyvind Boyesen. He showed me that matching the cases and cases to cylinder is just part of the process of getting a great flowing motor. Then put a good shine into it. Takes time but it works sweet. Especially if you are using race fuel.
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captmoto 1/22/2019 12:48pm
1/22/2019 12:48pm
This goes back to the old days when cases were real rough and not built with the precision they are today. I know my Elsinore cases were off and benefited from matching. My YZ465 was really pretty close and didn't need anything. My 05CR250 was spot on.
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Derek Harris 1/22/2019 1:18pm
1/22/2019 1:18pm
I've yet to see any power from what is sold and called matched cases in two strokes
I've seen no difference in power from large intentional mismatches to try and test various ideas.

Power is 99 percent from the port layout/transfer ducts and how well that gets matched to a pipe, ignition curve, and head.

power has climbed quite a bit since 1975 or 1980 but port widths and heights haven't hardly changed. The technology that has changed is very minute and iterative.

The worlds fastest 125 cc had a lot of cool things. One thing it did not have was polished cases, polished ports, perfectly matching cases to cylinder interactions or "turbo cranks", "stuffed cases etc. What it did have was some of the smartest, hardest working, 2 stroke minds on the planet and 40 years of effort behind it. IT produced over 55 hp when the honda gp effort was around 45 at the same time. To this day it turned faster lap times than the GP moto3 250f efforts at a far lessor price

Call me crazy - or data driven - but I also have NOT seen any shop make sure all the bearing holes are on axis etc when doing what they call matching cases.

The question becomes - if the holes are OFF - how do you fix? Welding and remachining isn't suitable
Sleeving is generally not doable
potentially one could find a larger bearing OD...

but unless you had access to blank cases that hadn't been machined - the cost of truly doing this right would more than any mortal would wish to pay.

Then you have to ask - how far off are the OEM cases - and why would an OEM NOT pay extra special attention to this - it would cause a host of warranty problems.

I personally have been impressed how accurate the OEMS are - but then again with CNC's - and modern fixturing - anything that is off is a gross mistake along many steps of the manufacturing process.

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FreshTopEnd
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FreshTopEnd 1/22/2019 2:13pm
1/22/2019 2:13pm
Derek Harris wrote:
I've yet to see any power from what is sold and called matched cases in two strokes I've seen no difference in power from large intentional...
I've yet to see any power from what is sold and called matched cases in two strokes
I've seen no difference in power from large intentional mismatches to try and test various ideas.

Power is 99 percent from the port layout/transfer ducts and how well that gets matched to a pipe, ignition curve, and head.

power has climbed quite a bit since 1975 or 1980 but port widths and heights haven't hardly changed. The technology that has changed is very minute and iterative.

The worlds fastest 125 cc had a lot of cool things. One thing it did not have was polished cases, polished ports, perfectly matching cases to cylinder interactions or "turbo cranks", "stuffed cases etc. What it did have was some of the smartest, hardest working, 2 stroke minds on the planet and 40 years of effort behind it. IT produced over 55 hp when the honda gp effort was around 45 at the same time. To this day it turned faster lap times than the GP moto3 250f efforts at a far lessor price

Call me crazy - or data driven - but I also have NOT seen any shop make sure all the bearing holes are on axis etc when doing what they call matching cases.

The question becomes - if the holes are OFF - how do you fix? Welding and remachining isn't suitable
Sleeving is generally not doable
potentially one could find a larger bearing OD...

but unless you had access to blank cases that hadn't been machined - the cost of truly doing this right would more than any mortal would wish to pay.

Then you have to ask - how far off are the OEM cases - and why would an OEM NOT pay extra special attention to this - it would cause a host of warranty problems.

I personally have been impressed how accurate the OEMS are - but then again with CNC's - and modern fixturing - anything that is off is a gross mistake along many steps of the manufacturing process.

With vertically split crank cases two strokes I have only heard "matching the cases" referring to the matching the transfer ports passages where they meet at the cylinder and centercases.

Truing bearing bores (buying matched cases) is something I have not heard referenced in this context, and more a legacy of older four bangers. I don't recall any manufacturer of a two stroke I've owned mandate buying centercases as a matched set.
Jrewing
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Jrewing 1/22/2019 2:18pm
1/22/2019 2:18pm
That engine would be around 60hp now I reckon, if not more if development continued.
But it was rotary valve where as Honda was reed.
Yz229
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Yz229 1/22/2019 2:46pm
1/22/2019 2:46pm
I would say not really useful to do unless going big bore/stroker. That's what I did on my YZ315 stroker. Low end volume was increased to get top end back. Much more power then my big bore only YZ295.

Would like to hear Derek Harris's opinion on this when increasing displacement from stock.
Derek Harris 1/22/2019 3:01pm
1/22/2019 3:01pm
FreshTopEnd wrote:
With vertically split crank cases two strokes I have only heard "matching the cases" referring to the matching the transfer ports passages where they meet at...
With vertically split crank cases two strokes I have only heard "matching the cases" referring to the matching the transfer ports passages where they meet at the cylinder and centercases.

Truing bearing bores (buying matched cases) is something I have not heard referenced in this context, and more a legacy of older four bangers. I don't recall any manufacturer of a two stroke I've owned mandate buying centercases as a matched set.
Im aware of both.

Most places that "match cases" match the case to the cylinder or cylinder to the case or some varient of both.
Most places that "match" cases often match the case to the gasket and the cylinder to the gasket ( a little dumb IMHO)

Some OEMS require both cases be bought together

Some or most now days sell the cases individually.

In a pure racing context - making sure all the holes are on axis to a tight tolerance would be ideal - and what any high level team would aspire to. Some bikes Do run better than other out of the crate - and certainly this could be one of those reasons.

I have read some shops that claim they do this when matching cases - but never asked or have witnessed how it was done.


In any case - I'll still contest that matching the transfers to the cases is a massive waste of time.
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newmann
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newmann 1/22/2019 4:20pm
1/22/2019 4:20pm
Holy old thread! Someone must have thought matched cases were important in 1978. Of course, sand cast magnesium cases in the quantity of a dozen or two probably took a little extra attention to detail.





zehn
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zehn 1/22/2019 4:48pm
1/22/2019 4:48pm
What 125 produced 55 hp?
rmgsxr
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rmgsxr 1/22/2019 5:29pm
1/22/2019 5:29pm
zehn wrote:
What 125 produced 55 hp?
I think Burt Munro built it.
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ama530
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ama530 1/22/2019 5:30pm
1/22/2019 5:30pm
zehn wrote:
What 125 produced 55 hp?
125cc road race engines. They also have a 1000rpm wide powerband. Wide open or not at all.
zehn
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zehn 1/22/2019 5:31pm
1/22/2019 5:31pm
zehn wrote:
What 125 produced 55 hp?
ama530 wrote:
125cc road race engines. They also have a 1000rpm wide powerband. Wide open or not at all.
I know, I guess I meant who built it, when/where was it raced etc.
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barnett468 1/22/2019 6:13pm
1/22/2019 6:13pm
zehn wrote:
What 125 produced 55 hp?
ama530 wrote:
125cc road race engines. They also have a 1000rpm wide powerband. Wide open or not at all.
zehn wrote:
I know, I guess I meant who built it, when/where was it raced etc.
I don't know who built the 55 hp 125 but this one did 187 mph in a world record run.

https://www.youtube.com/watch?v=Vz_r_3yqqR4
ama530
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ama530 1/22/2019 6:26pm
1/22/2019 6:26pm
The Aprilia 125 GP bikes made between 50-60HP. They were last raced in 2011. The Honda RS125 made 44HP out of the crate.
Jrewing
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Jrewing 1/22/2019 6:51pm
1/22/2019 6:51pm Edited Date/Time 1/22/2019 6:51pm
zehn wrote:
What 125 produced 55 hp?
ama530 wrote:
125cc road race engines. They also have a 1000rpm wide powerband. Wide open or not at all.
No they don’t. They have quite a big power band, just very high up. Purple too it was that they used haha
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CPR
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CPR 1/22/2019 11:29pm
1/22/2019 11:29pm
MxSkillz wrote:
Hey guys.. i was just wondering if anybody with any bike that has a few mods done has had their cases matched with their cylinder and...
Hey guys.. i was just wondering if anybody with any bike that has a few mods done has had their cases matched with their cylinder and gasket as part of their mods?.. Do you think this mod helped with the performace of the motor? Is it worth it to do? Did you feel a difference and can you explain how?

I see almost all engine tuners offer this service and was just wondering what it does to help? To me it sounds like its helps with having no restrictions for fuel flow.. which in turn will help performance.. just wondering and want to hear from people who have done this.. thanks
Hey MxSkillz you didn't say what engine? I'm assuming the CR in your photo.....most modern two stroke engines are pretty good casting wise. If you're doing a full on job, sure you can get rid of any flaws and match things up but any possible gains will be very very minor. Best bang for buck mods are combustion chamber shape and squish, pipe and ports if needed. Anything else is a luxury.

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