Long rod pistons

[Jack]

Jack can you give any tips that a guy at home can do to a 650 head, intake/ exhaust ports with a Dremel with a flex shaft and bits?

Dave,when you're limited to just stones rather than the ideal carbide cutters,patience will be the key using the dremel do to the lengthy time evolved using stones. There's a fair amount to be removed from the exhaust port roof or you could send the head to me and I'll work the the head, no charge for the porting service with the exception of the valve job work,cleaning and return shipping. You'll need to come up with 750 Virago exhaust valves for me to cut down as they are a key component in the flow department and if you like you can include the intake valves too(Virago 750),good valve springs and guides if replacement is needed. But most important I need feed back,good or bad but i'm confident the latter of the two won't be an issue at all but a "Big Impressional Grin" PM me if interested and we'll discuss it more.

 

[hotdog]

Crank assembly completed yesterday, 277 degree, tig welded pins, cr500 modded rods.
(Tig gurus dont be hatin my welds, I need to practice)

Preclean prior to assembly, yes the bearing came off prior to welding the pin.

[/IMG]

Inside of pins welded.

[/IMG]

Pressed inner wheels together & welded centre spline.

[/IMG]

Pre-assembly greasing.

[/IMG]

One side done.

[/IMG]

Pressing outer wheel on.

[/IMG]

10 seconds here saves a lot of flogging with the copper hammer.

[/IMG]

Truing crank in my adjustable jig.

[/IMG]

Completed crankshaft.

[/IMG]

Bead blasting of cases is next.

 

[Jack]

Looking good have you decided what head you're gonna use? Chucked my head in the mill last week to begin the D intake process,ports were shifted big time but nothing the old mig can't handle

 

[hotdog]

Looking good have you decided what head you're gonna use? Chucked my head in the mill last week to begin the D intake process,ports were shifted big time but nothing the old mig can't handle

Just secured a set of Forged True (256) standard bore pistons (still in the original boxes with install instructions) minus pins. Wanna trade a ported head.?

 

[Jack]

Just secured a set of Forged True (256) standard bore pistons (still in the original boxes with install instructions) minus pins. Wanna trade a ported head.?

Why all a sudden are these F/T pistons coming out of the closet My combination is based off 78MM.

 

[hotdog]

Just saw them and had to grab them...if I dont use them I'll move em on.

 

[hotdog]

Some forged true piston porn for you all, these are not going into the LR750. Just thought I would share some pics since they arrived today.
They are 75mm (+.025) 256 pistons.

256 forged true pistons

Forged true pistons 256 75mm + .025

Forged true pistons 256

Underside 256 f/t piston

Forged true 256 piston

F/T 256 piston weight = 159 grams

F/T 256 piston

 

[650performance]

FYI, those are '70s style race pistons and have over 11 - 1 c.r.

 

[hoffman900]

FYI, those are '70s style race pistons and have over 11 - 1 c.r.

They sure look like it! They look really heavy, too. How much ignition timing do you have to run with a set of pop-ups like that... 38-40 degress advanced?! Is anyone welding some quench pads on the xs heads?

 

[hotdog]

They sure look like it! They look really heavy, too. How much ignition timing do you have to run with a set of pop-ups like that... 38-40 degress advanced?! Is anyone welding some quench pads on the xs heads?

Added an additional picture including one weighed up = 159 grams bare.

Regards.

 

[Jack]

Those F/Ts are for the XS1 "70" combustion chambers(best head Yamaha ever produced and they dropped it) not the later style

 

[Jack]

They sure look like it! They look really heavy, too. How much ignition timing do you have to run with a set of pop-ups like that... 38-40 degress advanced?! Is anyone welding some quench pads on the xs heads?

I have a head in the works using KZ 78MMs pistons.The most combustion chamber reduction you can go is from 63CCs down to 53CCs without severely shrouding the valves. Flow testing as revealed little effects of intake flow but the exhaust seems to flatten some from around .350 to max lift

 

[hoffman900]

I have a head in the works using KZ 78MMs pistons.The most combustion chamber reduction you can go is from 63CCs down to 53CCs without severely shrouding the valves. Flow testing as revealed little effects of intake flow but the exhaust seems to flatten some from around .350 to max lift

Jack,

Have you looked at the Kaase Boss Nine heads? http://www.jonkaaseracingengines.com/index.php?option=com_content&view=article&id=219

Exhaust should be able to be taken care of with a more efficient exhaust system (a modern high velocity, tuned length type, not the oversized set-ups most are running).

 

[Jack]

Jack,

Have you looked at the Kaase Boss Nine heads? http://www.jonkaaseracingengines.com/index.php?option=com_content&view=article&id=219

Exhaust should be able to be taken care of with a more efficient exhaust system (a modern high velocity, tuned length type, not the oversized set-ups most are running).

The one factor that limits any major combustion chamber altercations is the chambers depth and volume. You're pretty much limited to a bath tube design along the lines of a Branch harley chamber. I'll see if I can find a old photo,remind you, this was a prototype head on the rough side

 

[Jack]

Here's my welded up prototype chamber for my long rod. By moving the valve close to center of the bore,the piston should theoretically pull harder on the port creating higher
vacuum pressure and port velocity.

 

[racerdave]

Dave,when you're limited to just stones rather than the ideal carbide cutters,patience will be the key using the dremel do to the lengthy time evolved using stones. There's a fair amount to be removed from the exhaust port roof or you could send the head to me and I'll work the the head, no charge for the porting service with the exception of the valve job work,cleaning and return shipping. You'll need to come up with 750 Virago exhaust valves for me to cut down as they are a key component in the flow department and if you like you can include the intake valves too(Virago 750),good valve springs and guides if replacement is needed. But most important I need feed back,good or bad but i'm confident the latter of the two won't be an issue at all but a "Big Impressional Grin" PM me if interested and we'll discuss it more.

Thanks for your offer Jack. I will keep this in mind. One question, on the Virago valves? Any year in particular? I did check a Yamaha dealer site that I have used before for snowmobile parts, I picked a 95 Virago, valves are still available.

 

[Jack]

No particular year,just make sure they're 750 Virago valves

 

[650performance]

Hoff -
The all in ignition timing for those pistons with a 40 cam averaged 36 degrees. I never heard of anyone who used more than 37. They used more lead on bikes set up for TT and shorter ovals and less lead, e.g. 33 - 35 on the longer tracks.
Yes, they are heavy but virtually indestructible. Note the old style thick rings.

 

[hoffman900]

Hoff -
The all in ignition timing for those pistons with a 40 cam averaged 36 degrees. I never heard of anyone who used more than 37. They used more lead on bikes set up for TT and shorter ovals and less lead, e.g. 33 - 35 on the longer tracks.
Yes, they are heavy but virtually indestructible. Note the old style thick rings.

That would make sense as you are full throttle a lot longer on the bigger ovals.

Jack,

Looking forward to seeing your results.

 

[hotdog]

Its been a while since I've had time to do much on this. Had an attempt at cleaning up the standard ports & chamber today to try & minimize some of the valve shrouding.

I don't have or have access to a flow bench & this is probably as far as I'd like to go with this as I dont want to be going backwards.

As you can see I have cleaned up the standard ports to get rid of the factory casting mess & smoothed out the bowl to seat transitions to try & get things flowing a bit better, any input/constructive criticism appreciated.

[/IMG]

Had this to start with, you can see the irregular casting between seat & bowl pocket.

Chamber before modification.

[/IMG]

You can see here the the material removed from the seat/bowl transition & the DE-shrouding of the valves.

[/IMG]

Hopefully it might flow a bit better than a stocker.

[/IMG]

Port cleaned up.

[/IMG]

Looking nice & shiny.

Tomorrow the plan is to have the guides installed after a few tiny more touch ups & then a 3/4 angle valve job after I get my valves faced & tipped.

Regards.