light weight pistons

worntorn said:
Iirc ,Jim Comstock has used Emgo pistons by the bucket load for his rebuilds, but the circlips that come with them must be replaced with better circlips. I can find the part number for the circlip if you are interested. I bought some for the RGM 920 pistons I used on the lightweight bike.

Glen
Click to expand...
Here it is
www.mcmaster.com

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.
www.mcmaster.com www.mcmaster.com
 
MAP Cycle pistons are manufacture in the USA according to MAP and the Google. Not that anyone other than myself would bother to look it up after Jim implied they are made in China. I read the Klaus story. Basically it just makes me think the longer skirts on the EMGO pistons for stock rods would be good on a street bike that was not going to get thrashed often. I'll have to go measure the MAP long rod pistons I took out of my engine to see if the the pair I bought are out of spec.

Good to know that the EMGO pistons are able to do the job on stock rods. Thanks Glen
 
Schwany said:
MAP Cycle pistons are manufacture in the USA according to MAP and the Google. Not that anyone other than myself would bother to look it up after Jim implied they are made in China. I read the Klaus story. Basically it just makes me think the longer skirts on the EMGO pistons for stock rods would be good on a street bike that was not going to get thrashed often. I'll have to go measure the MAP long rod pistons I took out of my engine to see if the the pair I bought are out of spec.

Good to know that the EMGO pistons are able to do the job on stock rods. Thanks Glen
Click to expand...
Their website says that MAP is the manufacture but MAP makes neither pistons or rods. Their website says their rods are sourced and designed by "High Cotton Power". Below is the info on High Cotton Power:

High Cotton PowerMilwaukee School of Engineering. Anderson
“Started a small vintage motorcycle parts business based in Chongqing China. Responsible for all of the design/engineering work. Also responsible in directing other purchasing agents in the procurement of the vintage motorcycle components. Have designed and supplied US based distributor with forged connecting rods and various intake manifolds. The connecting rods were designed complete with FEA analysis. Manifolds were designed using CFD analysis. Looking into expanding into the procurement of specially design crankshaft and cylinder heads. Parts are being sourced from different suppliers around various parts of China.”

Longjian auto parts co. ltd in Guangzhou China says they provided the MAP pistons but they may not anymore. There are no piston companies in the US that make them that cheap.
 
Last edited:
jseng1 said:
Their website says that MAP is the manufacture but MAP makes neither pistons or rods. Their website says their rods are sourced and designed by "High Cotton Power". Below is the info on High Cotton Power:

High Cotton PowerMilwaukee School of Engineering. Anderson
“Started a small vintage motorcycle parts business based in Chongqing China. Responsible for all of the design/engineering work. Also responsible in directing other purchasing agents in the procurement of the vintage motorcycle components. Have designed and supplied US based distributor with forged connecting rods and various intake manifolds. The connecting rods were designed complete with FEA analysis. Manifolds were designed using CFD analysis. Looking into expanding into the procurement of specially design crankshaft and cylinder heads. Parts are being sourced from different suppliers around various parts of China.”

Longjian auto parts co. ltd in Guangzhou China says they provided the MAP pistons but they may not anymore. There are no piston companies in the US that make them that cheap.
Click to expand...
They and Google sure fooled me then. They are still selling whatever long rod piston stock they have left for $299 a pair with rings, pins and clips. I guess it is the last of the Chinese long rod pistons MAP have assuming anything I read is true anymore. I should get out in the garage and look to see if they have made in China stamped on the box or inside the pistons anywhere. I think I already did that and they don't. Those sneaky guys.

I'm using your long rods, pistons, valves, and beehive springs currently and the parts are still functioning.
 
jseng1 said:
Their website says that MAP is the manufacture but MAP makes neither pistons or rods. Their website says their rods are sourced and designed by "High Cotton Power". Below is the info on High Cotton Power:

High Cotton PowerMilwaukee School of Engineering. Anderson
“Started a small vintage motorcycle parts business based in Chongqing China. Responsible for all of the design/engineering work. Also responsible in directing other purchasing agents in the procurement of the vintage motorcycle components. Have designed and supplied US based distributor with forged connecting rods and various intake manifolds. The connecting rods were designed complete with FEA analysis. Manifolds were designed using CFD analysis. Looking into expanding into the procurement of specially design crankshaft and cylinder heads. Parts are being sourced from different suppliers around various parts of China.”

Longjian auto parts co. ltd in Guangzhou China says they provided the MAP pistons but they may not anymore. There are no piston companies in the US that make them that cheap.
Click to expand...
Exactly.
 
Schwany said:
Indeed all the lighter weight high zoot pistons are expensive. Look on the MAP Cycle site. They sell complete piston sets at a reasonable price. I've recently been thinking about putting their pistons on my stock rods and lowering the compression of my 750. It is a real PITA to kick start the way it is built today. Stops my kicking leg due to high compression. Drives me nuts. First world problems from getting old.
Click to expand...
You might install compression releases in your 750
 
seattle##gs said:
You might install compression releases in your 750
Click to expand...
Did I actually post that? I need a check up from the neck up.

All I would actually do, if I ever get around to doing anything about it, is use a .040 copper head gasket. There is an .021 copper head gasket in the engine now without a barrel base gasket. I think I have an .030, but it may not be enough. I would be disappointed if I put lower compression pistons in my build. It would be a mistake. It was a dumb thing to say. I won't add compression releases. Would be a PITA modification.

For the record esteemed members, I never said MAP manufactures long rod pistons or long rods. I did repeat what they say about the pistons being made in the USA. Still not sure if that actually is false. The guy that corrected me doesn't manufacture pistons or rods either. Seems like a silly thing to even mention. I have no skin in parts game though and no reputation protect.
 
Schwany said:
Did I actually post that? I need a check up from the neck up.

All I would actually do, if I ever get around to doing anything about it, is use a .040 copper head gasket. There is an .021 copper head gasket in the engine now without a barrel base gasket. I think I have an .030, but it may not be enough. I would be disappointed if I put lower compression pistons in my build. It would be a mistake. It was a dumb thing to say. I won't add compression releases. Would be a PITA modification.

For the record esteemed members, I never said MAP manufactures long rod pistons or long rods. I did repeat what they say about the pistons being made in the USA. Still not sure if that actually is false. The guy that corrected me doesn't manufacture pistons or rods either. Seems like a silly thing to even mention. I have no skin in parts game though and no reputation protect.
Click to expand...
Jim is obviously, and rightly, proud of the fact he sells top quality US made products. These are from very well renowned manufacturers within the Motorsport world who supply NASCA etc.

So when someone undercuts him using cheaper imported parts, it’s understandable he wants to point out the difference.

This doesn’t mean no-one should buy the others, or everyone should buy his, just that folk should know what they’re buying.
 
Fast Eddie said:
Jim is obviously, and rightly, proud of the fact he sells top quality US made products. These are from very well renowned manufacturers within the Motorsport world who supply NASCA etc.

So when someone undercuts him using cheaper imported parts, it’s understandable he wants to point out the difference.

This doesn’t mean no-one should buy the others, or everyone should buy his, just that folk should know what they’re buying.
Click to expand...

I'm well aware of who is making Jim's parts. I think his long rod kit parts are better, but they are just another option.

I've used both, and there is not any difference in use on a street bike. Although I had other issues when I used the MAP parts. Everything was great until I installed some filters I had laying around that were too small and when I did that I pinched the float bowl tube to atmosphere, which caused a lean condition at larger throttle openings. Engine got darn hot WOT for any extended time. Fortunately I fixed all that when I reinstalled the JSM long rods again and some new JSM long rod pistons. Sorry about the little bit of my reality.

Who had the long rod kits first, MAP or JSM?

How many people other than Klaus have had MAP long rod piston failures?

MAP sells similar parts for Triumphs. Same rods for strokers I think. Have those Triumph kit parts also failed a lot?
 
Last edited:
Schwany said:
I'm well aware of who is making Jim's parts. I think his long rod kit parts are better, but they are just another option.

I've used both, and there is not any difference in use on a street bike. Although I had other issues when I used the MAP parts. Everything was great until I installed some filters I had laying around that were too small and when I did that I pinched the float bowl tube to atmosphere, which caused a lean condition at larger throttle openings. Engine got darn hot WOT for any extended time. Fortunately I fixed all that when I reinstalled the JSM long rods again and some new JSM long rod pistons. Sorry about the little bit of my reality.

Who had the long rod kits first, MAP or JSM?

How many people other than Klaus have had MAP long rod piston failures?

MAP sells similar parts for Triumphs. Same rods for strokers I think. Have those Triumph kit parts also failed a lot?
Click to expand...
I came out with the long rods first.

I was also the first to describe the advantages on my website with the text below:

A) More power: The increase in power is a result of more dwell time at the top of the compression stroke, allowing more time for the fuel charge to burn completely and exert maximum force on the piston throughout the power stroke, This translates to more power for the amount fuel you burn.

B) Less Vibration: More dwell time at the top and bottom of the piston strokes means less “snap” due to the pistons not having to stop and reverse direction as quickly and abruptly as they would with a shorter rod. The longer rod allows us to make the piston shorter and lighter.

C) Less stressful wear: The longer JS rod has less angle when traveling through mid-stroke than the short stock length rod. This means that less side forces are being applied to the cylinder wall – thus reducing friction, heat and wear.

The other big thing is the bushless rods. This saves about 15 grams on the small end without the bronze bushing which works only when using a DLC pin. You end up with a stronger lighter rod and reduced vibration. Nascars developed this and when I learned about it I knew I had to have it. The bike ran so much smoother that I decided to go into buisiness.
 
Last edited:
acadian said:
boys boys... please, let's all try to get along here
Click to expand...
You mean agree about everything? What would be the purpose of the forum if that were the case? Lonely hearts motorcycle club? ;)

I was looking around at other piston and rod options for "the people" not me, and when I went to the TGA site I noticed there is a change in philosophy regarding crank balancing with TGA's standard length Carrillo rods without the bush and the pistons TGA sells for them. TGA sounds like JSM in that regard now. I found that surprising. Plus there was this:

"A word of caution: If you think that changing the con rod geometry is going to drastically transform the characteristics of your engine, you have either had too many Buds or else believe too much of the hyperbole on the web. In simple terms, and not going to get into a detailed analysis of engine design here, longer rods reduce the loads on piston skirts due to reduced attack angles but shorter rods improve accelleration. There is a preference in the USA for long rods, but if you look at the latest Moto GP engines you will see that designers there do not subscribe to that view point. At the end of the day 'you pays yer money & makes yer choice'!"

Anyway, TGA pricing is higher than JSM pricing, so who's cheaper now? lol

It's all about informing the gen pop.

Speaking of TGA and Molnar... Anybody want some JSM bolts for Molnar barrels for the cost of shipping.
 
Schwany said:
You mean agree about everything? What would be the purpose of the forum if that were the case? Lonely hearts motorcycle club? ;)

I was looking around at other piston and rod options for "the people" not me, and when I went to the TGA site I noticed there is a change in philosophy regarding crank balancing with TGA's standard length Carrillo rods without the bush and the pistons TGA sells for them. TGA sounds like JSM in that regard now. I found that surprising. Plus there was this:

"A word of caution: If you think that changing the con rod geometry is going to drastically transform the characteristics of your engine, you have either had too many Buds or else believe too much of the hyperbole on the web. In simple terms, and not going to get into a detailed analysis of engine design here, longer rods reduce the loads on piston skirts due to reduced attack angles but shorter rods improve accelleration. There is a preference in the USA for long rods, but if you look at the latest Moto GP engines you will see that designers there do not subscribe to that view point. At the end of the day 'you pays yer money & makes yer choice'!"

Anyway, TGA pricing is higher than JSM pricing, so who's cheaper now? lol

It's all about informing the gen pop.

Speaking of TGA and Molnar... Anybody want some JSM bolts for Molnar barrels for the cost of shipping.
Click to expand...
I did a ton of reading on the rod ratios and power a few years ago. This was when I was building the 1360 Vincent and could choose the rod ratio by using different components.
My take from that was rod ratio is one of those things where a fairly wide range is acceptable and changing within that range won't change power output much, if at all. By coincidence the rod ratio on the 1360 is identical to a stock Commando, 1.68.

The main reason for a long rod on a Norton is to reach up into a short piston, if you decide to go that route.

Glen
 
Last edited:
worntorn said:
I did a ton of reading on the rod ratios and power a few years ago. This was when I was building the 1360 Vincent and could choose the rod ratio by using different components.
My take from that was rod ratio is one of those things where a fairly wide range is acceptable and changing within that range won't change power output much, if at all. By coincidence the rod ratio on the 1360 is identical to a stock Commando, 1.68.

The main reason for a long rod on a Norton is to reach up into a short piston, if you decide to go that route.

Glen
Click to expand...
Just one piece of the power making puzzle. The TGA stock length Carrillo rod option is good but a bit pricey in my opinion. Jim should have the Carrillo rods without a bush up top made in stock length for his JE pistons and include DLC coated pins. Would be a good option to go along with a stronger lighter weight crank. Would it make more power without doing other things to the engine? No, but it would spin up to the meat of the cam quicker. That I can attest to.

Not looking for agreement from anyone. It's just talk based on doing things that seem to work for me.
 
Schwany said:
Just one piece of the power making puzzle. The TGA stock length Carrillo rod option is good but a bit pricey in my opinion. Jim should have the Carrillo rods without a bush up top made in stock length for his JE pistons and include DLC coated pins. Would be a good option to go along with a stronger lighter weight crank. Would it make more power without doing other things to the engine? No, but it would spin up to the meat of the cam quicker. That I can attest to.

Not looking for agreement from anyone. It's just talk based on doing things that seem to work for me.
Click to expand...
The articles that I read said just the opposite. They found that an engine with a short rod and low rod ratio, like a stock Norton, revved up a little quicker than a long rod motor but both made the same amount of power.
Their test was scientific- they went to the trouble of changing rods and pistons on a high performance v8 engine. They kept the compression ratio the same in both instances but altered the rod ratio from something like 1.6 to 2.0. Neither was really better than the other, except the slight improvement in the quickness of the rev up with the short rods ( no load revving). Strangely, that quickness in free revving did not translate into extra acceleration thru the quarter or measureable extra power on the dyno. It was a big job to make the changes, but it was as if they had changed nothing.

Glen
 
worntorn said:
The articles that I read said just the opposite. They found that an engine with a short rod and low rod ratio, like a stock Norton, revved up a little quicker than a long rod motor but both made the same amount of power.
Their test was scientific- they went to the trouble of changing rods and pistons on a high performance v8 engine. They kept the compression ratio the same in both instances but altered the rod ratio from something like 1.6 to 2.0. Neither was really better than the other, except the slight improvement in the quickness of the rev up with the short rods ( no load revving). Strangely, that quickness in free revving did not translate into extra acceleration thru the quarter or measureable extra power on the dyno. It was a big job to make the changes, but it was as if they had changed nothing.

Glen
Click to expand...
OK, but you could be agreeing with me and not know it.

I was talking about stock length Carrillo rods like TGA is selling and JE pistons which I believe are also stock skirt length, and a lighter weight crank. I know my P11 750 is a heck of a lot quicker today than it was with a stock engine in 1972. Would it be faster than a stock P11 in a quarter mile? Probably so considering how a stock P11 is geared. A stock P11 would run out of legs. A quarter mile is a long stretch of road for an old motorcycle to be WOT. I suck at drag racing though, so somebody else would have to pilot my rocket. 🤣 I think the same would be true with a stock 750 Commando. I had one and it was sort of docile.

I'm thinking the guys making 2000 plus HP on the drag race circuit are not doing it with stock engine parts. Maybe they are using a different kind of science. ;)
 
Schwany said:
OK, but you could be agreeing with me and not know it.

I was talking about stock length Carrillo rods like TGA is selling and JE pistons which I believe are also stock skirt length, and a lighter weight crank. I know my P11 750 is a heck of a lot quicker today than it was with a stock engine in 1972. Would it be faster than a stock P11 in a quarter mile? Probably so considering how a stock P11 is geared. A stock P11 would run out of legs. A quarter mile is a long stretch of road for an old motorcycle to be WOT. I suck at drag racing though, so somebody else would have to pilot my rocket. 🤣 I think the same would be true with a stock 750 Commando. I had one and it was sort of docile.

I'm thinking the guys making 2000 plus HP on the drag race circuit are not doing it with stock engine parts. Maybe they are using a different kind of science. ;)
Click to expand...
Yes, sorry I misread your post. For sure a lighter crank revs quicker.

Glen
 

Similar threads

jseng1
New Product - Lightweight pistons and pins for stock 961 rods
Replies
3
Views
341
TonyA
TonyA
hhh
JS lightweight pistons for stock rods in 850 balance factor change
2
Replies
22
Views
3,030
Hortons Norton
Hortons Norton
F
‘71 Norton ignition light staying on.
2
Replies
22
Views
1,326
Peter Restaino
P
jseng1
crankshaft bob weight
2
Replies
37
Views
5,274
acotrel
acotrel
L
Red warning light stays on while riding — 1969 Commando Fastback 750
Replies
15
Views
1,392
MichaelD
M
Back
Top