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Suzuki (and other brands) valve dimensions needed

  • Thread starter Thread starter Samikoo
  • Start date Start date
S

Samikoo

Guest
I'm having trouble finding valve dimensions from the great Internet. Some can be found here http://www.ferrea.com/Suzuki-Engine-Valves/p34286 , but not all.

It's easy to find the stem diameters and valve sizes, but the length is sometimes difficult to find. Are there any pages that would have all this information?

I'm looking for 23mm exhaust valves with a length of 88mm. Stem diameter is 5.5mm at the moment, but if I was to upgrade to bigger valves I might renew the valve guides at the same time so a change in stem diameter is not ruled out. Honda CB500 has 23mm exhaust valves with a 5.5mm stem, but the length is unknown.

Suzuki has some 26mm intake valves on 85-87 GSX-R 750 engines, but the length is mystery on these also.

I know I could always use blank valves, but I'm trying to find a cheaper alternative.

So, if you have information on valve dimensions and/or a link to a page that has, please post it here.

BTW, is there a measurable gain in flow when going from a 5.5mm stem to a thinner stem? Or are there any problem associated with this conversion? Rocker mods, hard-to-find valve guides or something else?
 
Yes, going to a thinner stem does help flow - provided all the ancillaries are sized accordingly. Valve guide, guide boss - if any - etc. Almost invariably you will have to make guides to suit. The smaller the OE stem was the less gain you will see by going smaller...5.5 to 5.0 is barely worth it unless the port layout is so cramped you can't make it wider. What's the engine you're working on ? Problems with smaller stems depend a lot on valve opening mechanism, some can put side thrust into the stem which is much worse with smaller stems...
 
The engine is an -83 GS750 ES. It has 5.5mm stems, and I was thinking if I can't find valves with the right stem diameter, I'd go smaller.

There should be enough meat in the head to widen the port where valve stem decreases flow area.

It looks like I could use Honda valves, their length is 92.3mm. If the image on the Kibblewhite website is correct, the extra length is above the cotter groove so I could shorten the valve stem. I haven't checked how long a valve the rockers can handle.

I don't think I'll gain much by enlarging the valves with stock cams and bore, but I assume going +1mm won't hurt port velocity too much.
 
Any ideas what the price for those might be? I try to go el cheapo when I can, that's why I was looking for replacement valves.
 
Samikoo said:
Any ideas what the price for those might be? I try to go el cheapo when I can, that's why I was looking for replacement valves.
Click to expand...

I think the normal price for stainless valves is around $27 each. They sell blanks so you can make the length what you want. If you send one to them they will take a blank and cut it to your size and put the grove where it needs to be. If not them then call Jay at APE.
 
OK, that's not bad. I think a blank would be the way to go. I can have the grooves machined at work and can back cut them myself if necessary. Now the hard part is to figure if I should go +1 or +2mm on the exhaust valves? I don't have access to a flow bench so I could try what works. There is only room for +1mm on the intake seats.
 
Samikoo said:
OK, that's not bad. I think a blank would be the way to go. I can have the grooves machined at work and can back cut them myself if necessary. Now the hard part is to figure if I should go +1 or +2mm on the exhaust valves? I don't have access to a flow bench so I could try what works. There is only room for +1mm on the intake seats.
Click to expand...
What size is the intake valve? You don't have to make the exhaust to big unless you are going to use No2
ok I see 27mm I would go with the 28/24mm
 
Last edited:
Intakes are 25mm and 21mm exhaust. I know I don't (propably) need bigger valves with standard bore/compression, I'm planning ahead for 890-910cc and a CR of maybe 10.5-11:1 and mild cams, preferably from a GS1150? (GSX1100EFE around here).

Would bigger valves hurt port velocity if nothing else changed? Minor porting would be done at the same time, mainly around the bowl/stem area.
 
If I were you I would stuff a 1200Bandit motor in there and call it done. They come stock with 1157cc and a 28.5/25 valve head and a lot of aftermarket parts available. I really like the Bandit motors and they can be found cheep. If you don't want to do something like that. I have a spare 83 GS750 head I would sell cheep. Then you could do what you want to without taking your bike apart until you were done with what you want to do to it.

J.D.
941-391-1410
 
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