Author Topic: Drawbacks to new valve springs?  (Read 1167 times)

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Offline jimbojangles

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Drawbacks to new valve springs?
« on: February 26, 2019, 09:04:46 AM »
Are there any benefits or drawbacks to installing KPMI valve springs in my CB350F while I have the motor apart? I'm replacing my top end gaskets with a set of NOS gaskets and don't want to take the motor apart again for a long time. (NOS gaskets are expensive)

While I have the head off I plan to clean it up and do some light porting. I hope to install a hotter cam at a later date, but thought I could be prepared for the cam by already having new springs installed. Will this cause me any problems or be a benefit in any way until the cam is installed? 

I'm not trying to make this bike fast, I know it's limitations. I'm just trying to make it surprise some people and sound awesome with the new cam. I like the idea of a mean little 350.
1974 CB350F
2013 VFR1200F

Offline Bankerdanny

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Re: Drawbacks to new valve springs?
« Reply #1 on: February 26, 2019, 09:21:10 AM »
Are you thinking that you want to raise the redline significantly? I can't see where there would be a benefit to swap out the OEM springs on a non-race engine.
"The problem with quotes on the Internet is that you never know if they're true" - Abraham Lincoln

Current: '76 CB750F. Previous:  '75 CB550F, 2007 Yamaha Vino 125 Scooter, '75 Harley FXE Superglide, '77 GL1000, '77 CB550k, '68 Suzuki K10 80, '68 Yamaha YR2, '69 BMW R69S, '71 Honda SL175, '02 Royal Enfield Bullet 500, '89 Yamaha FJ1200

Offline jimbojangles

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Re: Drawbacks to new valve springs?
« Reply #2 on: February 26, 2019, 09:44:36 AM »
Dynoman recommends new valve springs for all of the camshafts. It would be nice to raise the redline a bit, or at least have some insurance if I miss a shift at high rpm.
1974 CB350F
2013 VFR1200F

Offline jimbojangles

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Re: Drawbacks to new valve springs?
« Reply #3 on: February 26, 2019, 02:23:14 PM »
Thanks.

I've had this 350 for several years now and have rebuilt it from the frame up. It revs out so nice and actually sounds better to me than some bigger bikes I've had, I think a mild cam would only improve on that.

I just wasn't sure how stiff these valve springs are. I've read somewhere that stiff springs can cause the lifters and cam shafts to wear out prematurely.
1974 CB350F
2013 VFR1200F

Offline Jerry Rxman Griffin aka MuthaF'er

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Re: Drawbacks to new valve springs?
« Reply #4 on: February 26, 2019, 08:41:36 PM »
Dynoman recommends new valve springs for all of the camshafts. It would be nice to raise the redline a bit, or at least have some insurance if I miss a shift at high rpm.


Been there, done that, destroyed the engine, installed better springs, all good since

Some might say stiffer springs can cause a little more wear on the rockers and cam. I don't see any problems. Not like you're doing 50,000 a year.
As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)

Offline jimbojangles

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Re: Drawbacks to new valve springs?
« Reply #5 on: February 27, 2019, 08:22:36 AM »
Thanks Jerry. I figure it's easier to install the springs now while the head is off so that when I decide to play around with a cam all I have to do is pop the valve cover off and swap cams.  Its' 100 bucks in springs now to save me $100 in gaskets later. I just didn't want to want to do it if it was going to cause a bunch of wear and damage to my valve train.

Does anyone know what a safe redline is with better springs and one of the webcams for a cb350f? 
1974 CB350F
2013 VFR1200F

Offline BomberMann650

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Re: Drawbacks to new valve springs?
« Reply #6 on: February 27, 2019, 09:58:36 PM »
If you wish to surprise people with a mean sounding 350, best to rig up an external speaker and play the sound of a Panigale from your phone as you pull up.  ;) That’ll get their necks twisting  ;D

That was funny 😂😂