Get out the straight jacket

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Madness

This will be my second last hoorah with the P11 motor. LOL

I ordered a Molnar 750 crank and barrels bored for 73mm pistons. Plan is to hot up the P11 motor a little more next year. On the fence about getting the Molnar 750 cases. Andy says that my P11 cases can probably take a good beating on the street and not crack and fall apart with his crank and my other parts in it.

Point of the project is to build a mild compression pump gas motor that I can ride the way I want to ride it and not worry much about winding it up. Kind of whacky considering I could have bought a modern bike that does all that easily for what I have into it.

Will be reusing my Fred Barlow ported P11 head with the JSM springs and valves in it. Also sticking with the JS2 cam and BSA lifters. Will be using 73mm 8.5:1 pistons, a thin base gasket, and a .021 copper head gasket to get up in the 9's range. Head was surfaced long ago, so it should be possible.

Anywho, I will update this thread with pics and babble once in a while. Get me on your ignore list, or stay tuned.
 
Madness

This will be my second last hoorah with the P11 motor. LOL

I ordered a Molnar 750 crank and barrels bored for 73mm pistons. Plan is to hot up the P11 motor a little more next year. On the fence about getting the Molnar 750 cases. Andy says that my P11 cases can probably take a good beating on the street and not crack and fall apart with his crank and my other parts in it.

Point of the project is to build a mild compression pump gas motor that I can ride the way I want to ride it and not worry much about winding it up. Kind of whacky considering I could have bought a modern bike that does all that easily for what I have into it.

Will be reusing my Fred Barlow ported P11 head with the JSM springs and valves in it. Also sticking with the JS2 cam and BSA lifters. Will be using 73mm 8.5:1 pistons, a thin base gasket, and a .021 copper head gasket to get up in the 9's range. Head was surfaced long ago, so it should be possible.

Anywho, I will update this thread with pics and babble once in a while. Get me on your ignore list, or stay tuned.
Sounds good
Keep us posted
 
đź‘Ť

You may want to use sealant vs base gasket if you're looking to squeeze every ounce of compression
 
đź‘Ť

You may want to use sealant vs base gasket if you're looking to squeeze every ounce of compression
I had "or no base gasket" in my original draft text, but not sure I can actually get away with it, so deleted it. I might be able to do it with Permatex Right Stuff or similar.

Do you have a set of JSM long Carillo's in your engine now?

Yep, but will be using the MAP Cycle long rods and pistons on this build with the new crank and barrels. Unless I change my mind and get the 73mm pistons from Jim and reuse the Carrillo rods on the new crank. Still pondering it. Probably should use the JSM stuff although I already ordered the MAP parts. I'm attracted to shiny new things. LOL

The MAP rods are not the same at the small end and the wrist pin is not as nice as the JSM setup. Otherwise, the MAP long rods look like Carrillo rods. Not sure how much difference the MAP parts will make on a street bike. I suppose the bushing at the small end of the MAP rods could wear quicker and get noisy eventually. Don't want to over think it until I have the parts in my hands. Most of it should all be here in about 8 days. I'll start the over thinking process then.

Only worry at this point is if Andy Molnar bored the barrels for stock 73mm pistons. If he did, the bores will be sloppy, and I'll have piston slap with the short skirt pistons and have to find a better machinist than I used last time.
 
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I had "or no base gasket" in my original draft text, but not sure I can actually get away with it, so deleted it. I might be able to do it with Permatex Right Stuff or similar.



Yep, but will be using the MAP Cycle long rods and pistons on this build with the new crank and barrels. Unless I change my mind and get the 73mm pistons from Jim and reuse the Carrillo rods on the new crank. Still pondering it. Probably should use the JSM stuff although I already ordered the MAP parts. I'm attracted to shiny new things. LOL

The MAP rods are not the same at the small end and the wrist pin is not as nice as the JSM setup. Otherwise, the MAP long rods look like Carrillo rods. Not sure how much difference the MAP parts will make on a street bike. I suppose the bushing at the small end of the MAP rods could wear quicker and get noisy eventually. Don't want to over think it until I have the parts in my hands. Most of it should all be here in about 8 days. I'll start the over thinking process then.

Only worry at this point is if Andy Molnar bored the barrels for stock 73mm pistons. If he did, the bores will be sloppy, and I'll have piston slap with the short skirt pistons and have to find a better machinist than I used last time.
Yeah, I also went with the Molnar 750 cylinders. This ended up costing me an extra set of pistons from JSM as I had originally planned to use a set of stock barrels and so had gotten a set of .5mm OS pistons and had intended to have the cylinders bored to fit. I ended up getting a set of 73mm pistons, which I guess means I have a set of new OS pistons squirrelled away for whenever the 73's wear out... All that to say that the Molnar cylinders I got were stock sized. I've built many Japanese engines and am not bad at judging piston clearance by feel; 73mm JSM pistons are maybe just a hair looser in the bore than I would do on a Japanese air cooled single, but then I do tend to build the Japanese ones just a little on the tight side, so the JSM piston to Molnar cylinder fit is probably fine.

I considered going with the MAP Cycle parts myself before choosing JSM. I was not familiar with MAP at the time and in the end went with JSM because Carillo's reputation is first rte and the MAP rods appeared to be no names. I'll be really interested to see what your impressions are when you can compare them side-by-side.
 
If you’re going to the trouble and expense of new Molnar barrels then I’d slow down a little.

Molnar offer Nickasil bores which are awesome.

A bit of liaison between Jim and Andy and you should have precise info to give to Andy to provide you with perfectly sized Nickasil bores.

That would make for a sweet set up.

Unless it’s too late already… if so I’ll get me coat…
 
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Yeah, I also went with the Molnar 750 cylinders. This ended up costing me an extra set of pistons from JSM as I had originally planned to use a set of stock barrels and so had gotten a set of .5mm OS pistons and had intended to have the cylinders bored to fit. I ended up getting a set of 73mm pistons, which I guess means I have a set of new OS pistons squirrelled away for whenever the 73's wear out... All that to say that the Molnar cylinders I got were stock sized. I've built many Japanese engines and am not bad at judging piston clearance by feel; 73mm JSM pistons are maybe just a hair looser in the bore than I would do on a Japanese air cooled single, but then I do tend to build the Japanese ones just a little on the tight side, so the JSM piston to Molnar cylinder fit is probably fine.

I considered going with the MAP Cycle parts myself before choosing JSM. I was not familiar with MAP at the time and in the end went with JSM because Carillo's reputation is first rte and the MAP rods appeared to be no names. I'll be really interested to see what your impressions are when you can compare them side-by-side.
The MAP rods are I'm not sure where manufactured. Possibly the USA. They have a slightly rougher media blasted looking finish than the Carrillo rods (based on product images), are 11 grams heavier at the small end, and possibly lighter at the big end. The big end spec does not show bearing shell weight. Pistons with rings, pin, and clips are 11 grams heavier. Shell bearings are Clevite-Mahle.

MAP Cycle has been around in one form or another since the mid-70's. I'm not concerned about the quality as much as the weight difference. I probably won't notice squat though.

Andy Molnar said he would be disappointed if his crank did not make my motor run smoother. 75% balance factor for a rigid frame. I doubt he would be anywhere near as disappointed as I'll be at $3989.95US crank and barrels shipped to my front door. lol
 
If you’re going to the trouble and expense of new Molnar barrels then I’d slow down a little.

Molnar offer Nickasil bores which are awesome.

A bit of liaison between Jim and Andy and you should have precise info to give to Andy to provide you with perfectly sized Nickasil bores.

That would make for a sweet set up.

Unless it’s too late already… if so I’ll get me coat…
I sat on the fence from the get go on the nikasil. He talked me out of buying his cases that the nikasil barrels drop right into. The barrels would need machine work and might be too thin squeezing them into my old cases. It's also possible he doesn't have any nikasil barrels right now with the 73mm bore.

I should talk to him. He claims good oil and air filtering up to 100K miles is possible with nikasil. I already paid for it all, but maybe he'll do a set of nikasil if I beg and buy his cases. I probably should. I think he is out doing something else today and not minding the store. He hasn't responded to any email. He was all over my email into the wee hours last night over there right up until I paid for the parts. :)
 
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JS rods are lighter where it matters (small end) than other steel rods. And I believe his pistons are lighter than Map.

In fact, doesn’t he do extra light ones for up to 750?

Jus’ seems to me that you’re in too far to cut corners … s’all.

But seriously, it all sounds real Hot Rot. Really looking forward to following your progress on this.
 
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JS rods are lighter where it matters (small end) than other steel rods. And I believe his pistons are lighter than Map.

In fact, doesn’t he do extra light ones for up to 750?

Jus’ seems to me that you’re in too far to cut corners … s’all.
On paper the MAP rod small end and piston combined are 22 grams heavier than the JS parts. However, that lighter weight ship has not sailed yet. I can always buy the JS pistons in 73mm and reuse the Carrillo rods. If the Molnar bores are not too large for the JS road spec of +.0055 piston to cylinder clearance. Race spec is .0055 - .006 clearance.

I am curious to see what the 74mm Wiseco pistons that are in my motor now look like after only a couple thou miles. No hurry to pull the motor apart though it's too cold in my garage for old guy hands.

It's been a full work day since I ordered and paid for the barrels. I think I'll have to live with the iron liners.

I do agree with your assessment. I waited too long.
 
Just a thought for your new engine build plans… Andy Molnar is developing an 8 valve Norton head.

Jus’ sayin’ …
 
Classic Bike magazine June '88 has a road test on his 8 valve Commando, also a brief history. Seems Dennis Poore at NVT commisioned Piper in Kent to develop an 8 valve head for the Commando in '73/74, but it's 'on paper' performance didn't translate too well in the real world..
 
Classic Bike magazine June '88 has a road test on his 8 valve Commando, also a brief history. Seems Dennis Poore at NVT commisioned Piper in Kent to develop an 8 valve head for the Commando in '73/74, but it's 'on paper' performance didn't translate too well in the real world..
Yeah exactly, I think that’s what motivates Andy to pick it up and basically finish off the development. He has a lot of good 4 valve single experience under his belt now and I guess he can see the potential in an 8 valve Norton twin.
 
Yeah exactly, I think that’s what motivates Andy to pick it up and basically finish off the development. He has a lot of good 4 valve single experience under his belt now and I guess he can see the potential in an 8 valve Norton twin.
Fair play and good luck to the man..... Doug Hele and Norman Hyde were on the NVT team that compared the Piper offering to what the Thruxton race shop were doing with four valves and saw a 2hp midrange improvement with the sixteen valves, but no improvement at the top end.
The rider of Emery's bike pretty much concurred, power seemed to arrive sooner, but that was 'butt' dyno only...
Be interesting to see how yer man gets on.......
 
Fair play and good luck to the man..... Doug Hele and Norman Hyde were on the NVT team that compared the Piper offering to what the Thruxton race shop were doing with four valves and saw a 2hp midrange improvement with the sixteen valves, but no improvement at the top end.
The rider of Emery's bike pretty much concurred, power seemed to arrive sooner, but that was 'butt' dyno only...
Be interesting to see how yer man gets on.......
The limiting factor with this muti valve conversation on a factory motor will still be a test on the bottom end unless I've missed something
 
Fair play and good luck to the man..... Doug Hele and Norman Hyde were on the NVT team that compared the Piper offering to what the Thruxton race shop were doing with four valves and saw a 2hp midrange improvement with the sixteen valves, but no improvement at the top end.
The rider of Emery's bike pretty much concurred, power seemed to arrive sooner, but that was 'butt' dyno only...
Be interesting to see how yer man gets on.......
As with Triumphs vs Nourish, the 8 valve vs 4 valve thing has to be viewed as a holistic package.

The 4 valve head should facilitate a far more efficient combustion chamber, allowing higher CR without the downsides of pre igntion etc. 2 Valves per port means you can have a combination of flow AND velocity that’s not possible with a single valve and port. That also allows the use of much bigger carbs, again without the usual downside. All these changes then allow the use of very different cams. And so on.

So, just knocking up a head with 8 valves ain’t gonna do much. Designing the holistic package around 8 valves is a different matter entirely.

And there’s an awful lot more knowledge to pull from these days in this field.

It will certainly be interesting to see if Andy can nail it.
 
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