Topic: Setting Installed Height on CB750 valve springs

[bwaller]

70lbs would be good.

Just for the info an original stock 550 with 35 yr old springs yielded 42lbs at an installed height of 1.430". (I don't think that engine had ever been apart so seats had never been cut.) KPMI springs at that 1.430" made 62lbs. KPMI recommended an IH of 1.38-1.40 for their springs. So at 1.39" spring pressure was 70lbs. 

In this case following the recommended IH yielded seat pressures in the ballpark. So short of having access to a pressure gauge at least follow the spring manufacturers direction with IH. Springs shims are available.

[calikid]

70lbs would be good.

Just for the info an original stock 550 with 35 yr old springs yielded 42lbs at an installed height of 1.430". (I don't think that engine had ever been apart so seats had never been cut.) KPMI springs at that 1.430" made 62lbs. KPMI recommended an IH of 1.38-1.40 for their springs. So at 1.39" spring pressure was 70lbs. 

In this case following the recommended IH yielded seat pressures in the ballpark. So short of having access to a pressure gauge at least follow the spring manufacturers direction with IH. Springs shims are available.

Thanks for the reply! What if idont know the spring manufacturer? When i took the sprigs out the PO had shims in it already.. Should I install back with it? We did grind the seats and all that stuff so i don't know if that'll affect the height.

[calikid]

Pictures for reference!

[calikid]

Anyone else have insight on this!

[Don R]

I just went through a bout of failed springs on my Chevrolet race engine. We used the same manley spring that lasted 270 1/4 mile passes but with a new cam. The first set broke a spring at 30 runs the next set broke 2 springs by 39 passes. We learned the springs were set with too large an installed height and this allowed harmonics to break the spring. It seems the middle of the spring is moving opposite the ends. There is a required distance from coil bind that is required to keep the harmonics under control. We shimmed tighter and are hoping it's cured.
 That said on a 750 it may not be as big an issue due to the smaller mass of the spring.

[lucky]

Mike, none of the springs I've gotten from Kibble White have had installed height specified. I don't remember seeing that spec in the 1.5" think factory Honda service manual. I'll have to give it another look. The Kawasaki manual has 2 full pages devoted to the specs, the checking, the adjustments, and the tables on "installed height".

I'l like to know what they should be once known.

Regards,
Gordon

I'm doing Googles on "valve spring heights" and variants. Seems the car guys are really into this. Found a special micrometer just for this: http://www.jegs.com/p/JEGS/753947/12552/-1

Mike you may have slipped a decimal on my readings. If 1.34 is the target, and I'm at 1.45, I'll need a .060, .030 and a .015 to get close to the 1.34. Not just the .015.

What type of device is used to check the seat pressure? I'm googling that right now, nothing yet.

I'll report back what i may hear from APE once they open.

The "car" people use a tool to compress valve springs and it measures the amount of pressure or resistance of the valve spring to compress.


I have been working on motorcycles most of my life and we just buy new valve springs and install them. Go to any car machine shop and have them compress a valve spring and ask them how much pressure it took to compress a valve spring.
Probably 400 lbs?

http://www.toolsource.com/valve-spring-tester-0500-p-106529.html?gclid=CICfgZmz2rcCFUVyQgodwwkA3Q&sourceid=googleps

Got an extra $1300.00 bucks?

[MCRider]

A proper valve spring pressure tester can be had for less than $90. Just put it and the spring in a vice and squeeze.

http://www.ebay.com/itm/COMP-Cams-Valve-Spring-Tester-Mini-0-1000-lbs-in-Ea-5314-/330931643252?pt=Motors_Car_Truck_Parts_Accessories&hash=item4d0d102374&vxp=mtr

Bottom line is though, if you've got all new springs per Lucky, you likely can bypass this step. Unless you're a performance guy and everything needs to be dead on.

If you insist on using old springs you may want to test them to see that they are unform pressure. Shimming a weak one to match the others doesn't seem best practices to me however.

[lucky]

A proper valve spring pressure tester can be had for less than $90. Just put it and the spring in a vice and squeeze.

http://www.ebay.com/itm/COMP-Cams-Valve-Spring-Tester-Mini-0-1000-lbs-in-Ea-5314-/330931643252?pt=Motors_Car_Truck_Parts_Accessories&hash=item4d0d102374&vxp=mtr

Bottom line is though, if you've got all new springs per Lucky, you likely can bypass this step. Unless you're a performance guy and everything needs to be dead on.

If you insist on using old springs you may want to test them to see that they are unform pressure. Shimming a weak one to match the others doesn't seem best practices to me however.

I agree.... just use new springs and replace as a set.

[johno]

MCR to keep it simple,
Pick a spring pressure that suits your needs ,  bwaller and Rieks  spot on ( 70 lbs stock type cam to 80 lbs steetable hot type cams, maybe more for full race type 10k plus))

 you got the right tools to measure installed height, do that,  then take your springs and specs to the local engine recon shop ( every recon shop in America will have a spring tester ) get them to check each spring  ( use egg carton to keep springs seperate and numbered)  should take 30 minutes flat $ wise

Go home and shim under the base to the installed height , ( big jay system works well on more technical installs but too many measurements that can go wrong for the old honda measurements)

Then   install remembering to do three things,
1. Put the valve stem seals on..............it happens ask me.
2. close wound end of springs go to bottom ... both springs
3. After assembly tap the top of the valve to settle the collets and make sure alls well

Have a beer and worry about the next step..............only one though !