Topic: Yoshi 550 B Grind Cam

[bambuhiphop]

Hello All,

I am looking for some help. I have gotten my head all confused. I am wrapping up my motor build and just going back through everything as I want to make sure I'm not missing things. So I am asking stupid questions, haha.

I have an Isle of Man TT cam (b grind). I installed it per the manual. Cam notch is face forward looking at it from the #4 side. TDC is set and valve clearances are set based on manual. I was going through some notes on the cam and they got me wondering if I missed something. This is what I have notated.

Isle of Man cam Specs
In opens 27BTDC-closes 57ABDC lift 9.00mm
Ex opens 56BBDC-closes 27ATDC lift 8.55mm
Yoshi part# YH600-122-00
Valve clearance street-0.10mm race-0.15mm,
Ignition Timing +5 advance

The clearance and timing notes are what are confusing me...

1. Do I need to advance the time 5 degrees or does the cam cause a +5 and I need to retard timing?
2. 0.10mm would be 0.004. I set my clearance at 0.002 and 0.003 per the manual. Should I increase this because of the cam's more aggressive lobes?

[scottly]

1. Do I need to advance the time 5 degrees or does the cam cause a +5 and I need to retard timing?
The cam timing does not directly alter the ignition timing; the way I read that is to set ignition timing 5 degrees over stock, but that might not be the best setting for street use; I would use the stock ignition timing as a starting point.
2. 0.10mm would be 0.004. I set my clearance at 0.002 and 0.003 per the manual. Should I increase this because of the cam's more aggressive lobes?
I would set the clearance at the specs recommended by Yoshi.

[Rod]

Great cam, I like this profile. Timing is an additional 5 degrees advance on standard timing. Use the Yoshi timing and valve clearances, NOT the stock settings. Altering cam profiles can require changes to ignition timing, race cams effect the volumetric efficiency of the engine - its worse at lower rpm compared to stock, causing slower burn - within limits, this is compensated for by increasing the advance on the ignition.

[Bill/BentON Racing]

Yah,  use, Pop's specs. We ran .005 in and ex, this cam will light it up from @ 7K -13,000 rpms. What carbs you running and intake manifolds? Pop's usually used CR31s and HRC manifolds.

[bambuhiphop]

Yah,  use, Pop's specs. We ran .005 in and ex, this cam will light it up from @ 7K -13,000 rpms. What carbs you running and intake manifolds? Pop's usually used CR31s and HRC manifolds.

I am using CR26's from Powerbarn and stock manifolds that I had backcut to match the adapter spigots when the head went to mrieck. He did a stage 3 port. Pistons are DP592/61s's. Rods were shot peened and balanced with 750 blots and nuts. Crank was lightened and balanced.

I will increase my clearances. This is really going to be a street bike. Safe to go with the .004 or is .005 really where I should be?

Great cam, I like this profile. Timing is an additional 5 degrees advance on standard timing. Use the Yoshi timing and valve clearances, NOT the stock settings. Altering cam profiles can require changes to ignition timing, race cams effect the volumetric efficiency of the engine - its worse at lower rpm compared to stock, causing slower burn - within limits, this is compensated for by increasing the advance on the ignition.

Also, I have to claim a bit of ignorance on the advance (first time I've done this piece). I want to install the cam per the factory manual and then advance the timing with the C5 ignition I am running, correct?

[754]

You had said notch pointing forward, is that what the  manual shows? 
I know on a 750 it points up.

[bambuhiphop]

You had said notch pointing forward, is that what the  manual shows? 
I know on a 750 it points up.

Yes. Should be at the 3 o'clock (or 9) position per the manual.

[bwaller]

Sorry if I missed this but what pistons are you using? Plus not to upset you but did you degree the cam? Most often unless you find true TDC the cam can be off from suggested settings quite a bit. I've seen original TDC marks off .5 to a degree and more.

If you used a piston with some dome, you'll absolutely need to check valve/piston clearance to be safe.

That cam is similar to the Megacycle 126-20 with identical lobe centers and yes it's a good cam that is still easy on the valve train.

Good luck.

[bambuhiphop]

Sorry if I missed this but what pistons are you using? Plus not to upset you but did you degree the cam? Most often unless you find true TDC the cam can be off from suggested settings quite a bit. I've seen original TDC marks off .5 to a degree and more.

If you used a piston with some dome, you'll absolutely need to check valve/piston clearance to be safe.

That cam is similar to the Megacycle 126-20 with identical lobe centers and yes it's a good cam that is still easy on the valve train.

Good luck.

DP592/61s's.

Yes, I got True TDC and degreed the cam.

[Camrector]

Bambu I’m using the same cam on my 674cc CB650 motor. Head is ported and also using the c5 ignition. This cam is a beast and just doesn’t stop. I set the c5 to normal timing after degreeing in the cam. I’ll make changes at the dyno maybe, but as of now it’s so damn strong I don’t want to mess with it lol.
I did use the yoshi valve clearance numbers as well.

[bambuhiphop]

Bambu I’m using the same cam on my 674cc CB650 motor. Head is ported and also using the c5 ignition. This cam is a beast and just doesn’t stop. I set the c5 to normal timing after degreeing in the cam. I’ll make changes at the dyno maybe, but as of now it’s so damn strong I don’t want to mess with it lol.
I did use the yoshi valve clearance numbers as well.

Thanks Cam. Did you go .004 or .005 on the clearance?

Also, did you degree the cam +5 or did you install normal (stock) and are going to deal with the timing in the C5?

[Camrector]

.004
And left the advance normal until I get on the dyno and pkay with the c5.s settings

[bambuhiphop]

.004
And left the advance normal until I get on the dyno and pkay with the c5.s settings

Awesome. Thanks man! I will just need to up my clearances then. Cam is all set, phew.

Thanks a bunch for all the help everyone. Greatly appreciated!!