'58 RE Indian MPS-750-PF Build

[Grandpa Jones]

Looks and sounds good! You may want to check with the tech folks
about the "open" primary, they may want the holes covered to pre-
vent anything getting caught in the spinny bits.

Cheers, Dave

[panic]

1 3/8" primaries

Why?

[Scottie J]

Looks and sounds good! You may want to check with the tech folks
about the "open" primary, they may want the holes covered to pre-
vent anything getting caught in the spinny bits.

Cheers, Dave

Yes, I understand and acknowledge that.  My plan is to get some "perforated" sheet metal, cut and form it to the inside, paint it to match the tank, and then epoxy it into place with 3M automotive epoxy.  I'm now trying to get it dialed in and tuned, and then I will go back and finish off the odd bits and pieces.

1 3/8" primaries

Why?

Well, because that's the size that fits into exhaust port!       Bear in mind, I essentially have two 350 cylinders with a 71mm bore firing on opposite strokes.  It's not like I have big block Chevy trying to pump out 50+ ci of air per hole.  Besides, changing to the 2" collector has already opened up the exhaust so much over stock, I no longer have much bottom end.  Plus, the Amal carb has been rendered practically useless because the motor is now scavenging so well, it drew the entire fuel circuit dangerously lean.  The Amal 930 has a pressed pilot jet and is not replaceable, and it is so lean in the pilot circuit that the bike will run and idle with the air screw turned in tight and completely closed.  It should fall on it's face and die when that happens.  I have a friend that has a freshly rebuilt 34mm Keihin CV carb off of a Rebel 250 that I'm going to grab Tuesday afternoon.  he said to go ahead and try it out, and if it works, pay him $50, if it doesn't just drain it and bring it back.  I eventually will install a pair of Mikuni TM32's, but my funds are drained at the moment and need to hold off on that for the time being.

Anyways, here's a short video I put together yesterday.  The exhaust sounds killer!  Kind of actually sounds like an old race bike.   

https://www.youtube.com/watch?v=Q1ZnHlEXUFU&feature=youtu.be

[Scottie J]

Oh, also I have a lead on a nicely priced small fairing.  Nothing LSR type, but is functional and clean and will look good on my bike I think.  And it's only $125 shipped out with the fly screen.

[Queeziryder]

Looks and sounds good! You may want to check with the tech folks
about the "open" primary, they may want the holes covered to pre-
vent anything getting caught in the spinny bits.

Cheers, Dave

Yes, I understand and acknowledge that.  My plan is to get some "perforated" sheet metal, cut and form it to the inside, paint it to match the tank, and then epoxy it into place with 3M automotive epoxy.  I'm now trying to get it dialed in and tuned, and then I will go back and finish off the odd bits and pieces.

1 3/8" primaries

Why?

Well, because that's the size that fits into exhaust port!       Bear in mind, I essentially have two 350 cylinders with a 71mm bore firing on opposite strokes.  It's not like I have big block Chevy trying to pump out 50+ ci of air per hole.  Besides, changing to the 2" collector has already opened up the exhaust so much over stock, I no longer have much bottom end.  Plus, the Amal carb has been rendered practically useless because the motor is now scavenging so well, it drew the entire fuel circuit dangerously lean.  The Amal 930 has a pressed pilot jet and is not replaceable, and it is so lean in the pilot circuit that the bike will run and idle with the air screw turned in tight and completely closed.  It should fall on it's face and die when that happens.  I have a friend that has a freshly rebuilt 34mm Keihin CV carb off of a Rebel 250 that I'm going to grab Tuesday afternoon.  he said to go ahead and try it out, and if it works, pay him $50, if it doesn't just drain it and bring it back.  I eventually will install a pair of Mikuni TM32's, but my funds are drained at the moment and need to hold off on that for the time being.

Anyways, here's a short video I put together yesterday.  The exhaust sounds killer!  Kind of actually sounds like an old race bike.   

https://www.youtube.com/watch?v=Q1ZnHlEXUFU&feature=youtu.be

Scottie,
Have a read of the following, it WILL make the Amal 930 work for you.

http://www.jba.bc.ca/Bushmans%20Carb%20Tuning.html

Neil

[Scottie J]

Awesome!  Thanks for that Neil!  I had heard that you could ream the pilot hole, but I couldn't find out what size bit to use.  The carb is only 2 years old, so if for what ever reason it is clogged it is likely a small piece of rust from the tank.  I'll have to track down a bit and give that a try.  Tho, I am still kind of leaning towards the CV for street use.  Living in Denver I go thru some pretty drastic altitude changes when I go for serious rides up in the Rockies.  I live at about 5,300' and sometimes ride as high as 12,000' so you can see where the CV carb would have it's advantages.  I wouldn't likely use it on any track tho.

[SPARKY]

SJ  What a bitchin ride you have created---she sure sounded great pulling hard around that curve!!!!!!!!! 

[panic]

The usual pipe size is slightly larger than the exhaust valve.

[Scottie J]

SJ  What a bitchin ride you have created---she sure sounded great pulling hard around that curve!!!!!!!!! 

Thanks!       

The usual pipe size is slightly larger than the exhaust valve.

I don't know the exact diameter but the exhaust valve can't be much bigger than 1".

[panic]

Don't know if you have this:

http://tinyurl.com/lsg669w

[Scottie J]

Don't know if you have this:

http://tinyurl.com/lsg669w

I actually have the digital and paper copies.  But now I have it on my phone too.  Thanks!

[Scottie J]

Scottie,
Have a read of the following, it WILL make the Amal 930 work for you.

http://www.jba.bc.ca/Bushmans%20Carb%20Tuning.html

Neil

Neil - The other day I followed thru with the carb modification on the pilot hole/jet.  I didn't have a #78 bit but I did have a #60, which is only ever so slightly bigger.  I decided to go ahead with it as it is still within .040 and the pilot was extremely lean.  I used a pair of small vice grips to hold the bit and then I hand "drilled" it very carefully, removing a very slight amount of brass from the jet.  Now it's idling quite well again.

And actually, I've been having quite the adventure trying to dial the bike in.  Apparently my changes to the exhaust and compression made much bigger differences than I had anticipated, hence why the bike was running so lean.  But I was also having big trouble with detonation over the last week.  Factory timing is 34* BTDC but I could not get the bike to stop detonating until I was under 30* BTDC.  And at 29.5* it just didn't have any grunt to go.  So after some research and consulting my friend who runs on corn, and decided to do a 25%-75% pre-mix of E85 and 91oct.  It definitely helped, but was still detonating after the engine would get hot.  The other day while playing with the timing for over an hour, I once tickled the carb (the engine still hot from my test ride) and the fuel pretty much vaporized as it exited the carb.  Grab the carb mount on the intake side and it was hot as hell.  So yesterday, I ran to the local Brit parts supplier and bought a thermal spacer and installed it over my lunch.  After I clocked out, I fired up the bike and went for another shakedown run focusing on load timing instead of a light, bringing a couple of tools with to correct timing on the road side.  After the 3rd timing correction, she was purring like a kitten at idle and growling like a bulldog on the go.  I wasn't pulling any more than half throttle because of where I was, but man was she running really good.

Here's a 6 minute video, starting off with the final timing change, and then a short cruise thru where I work.


https://www.youtube.com/watch?v=eoOQ6SzEmwc

[fordboy628]

Scottie,
Have a read of the following, it WILL make the Amal 930 work for you.

http://www.jba.bc.ca/Bushmans%20Carb%20Tuning.html

Neil

Neil - The other day I followed thru with the carb modification on the pilot hole/jet.  I didn't have a #78 bit but I did have a #60, which is only ever so slightly bigger.  I decided to go ahead with it as it is still within .040 and the pilot was extremely lean.  I used a pair of small vice grips to hold the bit and then I hand "drilled" it very carefully, removing a very slight amount of brass from the jet.  Now it's idling quite well again.

And actually, I've been having quite the adventure trying to dial the bike in.  Apparently my changes to the exhaust and compression made much bigger differences than I had anticipated, hence why the bike was running so lean.  But I was also having big trouble with detonation over the last week.  Factory timing is 34* BTDC but I could not get the bike to stop detonating until I was under 30* BTDC.  And at 29.5* it just didn't have any grunt to go.  So after some research and consulting my friend who runs on corn, and decided to do a 25%-75% pre-mix of E85 and 91oct.  It definitely helped, but was still detonating after the engine would get hot.  The other day while playing with the timing for over an hour, I once tickled the carb (the engine still hot from my test ride) and the fuel pretty much vaporized as it exited the carb.  Grab the carb mount on the intake side and it was hot as hell.  So yesterday, I ran to the local Brit parts supplier and bought a thermal spacer and installed it over my lunch.  After I clocked out, I fired up the bike and went for another shakedown run focusing on load timing instead of a light, bringing a couple of tools with to correct timing on the road side.  After the 3rd timing correction, she was purring like a kitten at idle and growling like a bulldog on the go.  I wasn't pulling any more than half throttle because of where I was, but man was she running really good.

Here's a 6 minute video, starting off with the final timing change, and then a short cruise thru where I work.


https://www.youtube.com/watch?v=eoOQ6SzEmwc

Some general trends for engines, racing or otherwise:

1)  more compression ratio, less total timing required
2)  lower octane fuel, less total timing
3)  higher temperature, less total timing     (a chemical reaction speeds up at higher temperatures.    Cold engines can tolerate more timing, UNTIL they are warmed up.)
4)  lean mixture, less total timing
5)  reduced spark path length, less total timing    (projected nose plug Vs. regular nose   OR   regular nose Vs. retracted gap    etc)
6)  etc, etc

NORMALLY, reversing the situation reverses the timing equation.

What you do not want is: peak cylinder pressure prior to TDC.    Peak cylinder pressure should occur somewhat after TDC.    Although this is a sophisticated measurement requiring special instrumentation.
 
Fordboy

[Scottie J]

Some general trends for engines, racing or otherwise:

1)  more compression ratio, less total timing required
2)  lower octane fuel, less total timing
3)  higher temperature, less total timing     (a chemical reaction speeds up at higher temperatures.    Cold engines can tolerate more timing, UNTIL they are warmed up.)
4)  lean mixture, less total timing
5)  reduced spark path length, less total timing    (projected nose plug Vs. regular nose   OR   regular nose Vs. retracted gap    etc)
6)  etc, etc

NORMALLY, reversing the situation reverses the timing equation.

What you do not want is: peak cylinder pressure prior to TDC.    Peak cylinder pressure should occur somewhat after TDC.    Although this is a sophisticated measurement requiring special instrumentation.
 
Fordboy

Yeppers.  That's why I added the E85 and the thermal spacer to the carb, so I could balance the timing out and get a little advance back.  Tom Lyons, the Enfield specialist that I've been in contact with, is a very educated man when it comes to performance science.  I have had many hours of conversation with him over the phone and we have had this conversation before of what you just posted.  So fortunately, I was aware of these possible issues and is how I was able to diagnose the problem.  Between the increased cylinder pressure and hot 85oct fuel, it was a pure recipe for detonation.  I just wasn't aware that my fuel was getting so hot.  But it looks like I'm in the right direction and have it about as good as I can with the basically stock motor before I start building my performance motor.  But after putting the bike back together I've decided that I'm going to pull the heads again and replace the valve springs and the primary chain.  The springs are just old as hell and the primary chain looked like it's on it's way out the door, and I can't be having that.   

[RansomT]

How are you checking your air fuel ratio?