Topic: 750 5mm valve conversion

[ttr400]

Can anybody of you 750 guru's out there help with some info that I need.

i have the kibblewhite 5mm valve conversion kit and need to know the installed valve spring height, plus the installed length seat pressure.

Many thanks Kevin

[MRieck]

Kibblewhite says 1.370" to 1.380 Kevin.

[ttr400]

Thanks Mike, I searched all over the kibblewhite site and could not find those specs.! Any idea of spring pressure. 75lbs ? or more?

Kevin

[MRieck]

Thanks Mike, I searched all over the kibblewhite site and could not find those specs.! Any idea of spring pressure. 75lbs ? or more?

Kevin

75lbs will be enough Kevin. You are running that 125-75 if I remember correctly?

[ttr400]

Great. Yes the 125-75. thanks Mike.



Kevin

[turboguzzi]

mmm.... hows the reliability record with 5mm stems?

Can understand that with a dohc but with rockers and high lift your bound to increase big time side loading on the stem,

TG

[MRieck]

mmm.... hows the reliability record with 5mm stems?

Can understand that with a dohc but with rockers and high lift your bound to increase big time side loading on the stem,

TG

The valve/retainers are half the weight. You'd have to run about 1/3 more spring with the 6.5mm valves. The guide is so big and long it picks up heat, load etc. I was told this set up was tested to 14,000 RPM for extended periods with negligible wear on the guide, stem and rocker arm.

[MRieck]

mmm.... hows the reliability record with 5mm stems?

Can understand that with a dohc but with rockers and high lift your bound to increase big time side loading on the stem,

TG

How is the reliability with you stock 550 stuff?

[turboguzzi]

mmm.... hows the reliability record with 5mm stems?

Can understand that with a dohc but with rockers and high lift your bound to increase big time side loading on the stem,

TG

How is the reliability with you stock 550 stuff?

close to perfect i think

Didnt tear down after this last season but on all other tear downs valve play was in spec, and that's with guides cut to the port roof, at least on the inlet.

had some 93' GSXR750 valves laying around with tiny stems and the right diameters, they were tempting to use at the time but I skipped because of $$$ but also because they looked like they would simply buckle at one point...

[Sam Green Racing]

Ran them for 3 seasons in the CR Yossef, no issues what so ever.

Sam.

[simon#42]

had them in my f2 for a couple of years now , done just over 25,000 miles and all seems well . am hoping it will cure the guide wear problems , will run it for another year then have a look

[BLUE71TURBO]

  How much is this 5mm conversion ?   

[MCRider]

had them in my f2 for a couple of years now , done just over 25,000 miles and all seems well . am hoping it will cure the guide wear problems , will run it for another year then have a look

Just curious...What about converting to smaller stems would make one think they would wear less? Hard to make that sentence sound right. Its a sincere curiosity, not a poke.  And I hope they have given you better performance than stock.  Are they (valves and guides) of better material or such?

Am considering them for future project but its a K head.

[MRieck]

  How much is this 5mm conversion ?   

1,100.00 for forum members.  That includes 34mm intakes/28mm exhaust valves, guides,springs,Ti retainers,spring bases, keepers and lash caps

[MRieck]

had them in my f2 for a couple of years now , done just over 25,000 miles and all seems well . am hoping it will cure the guide wear problems , will run it for another year then have a look

Just curious...What about converting to smaller stems would make one think they would wear less? Hard to make that sentence sound right. Its a sincere curiosity, not a poke.  And I hope they have given you better performance than stock.  Are they (valves and guides) of better material or such?

Am considering them for future project but its a K head.

Much better material MC. Nice thing is the intake valve is 34mm (same as the F2) and when you open the seat up to 90% of the intake valve OD you start moving some charge.

[MCRider]

had them in my f2 for a couple of years now , done just over 25,000 miles and all seems well . am hoping it will cure the guide wear problems , will run it for another year then have a look

Just curious...What about converting to smaller stems would make one think they would wear less? Hard to make that sentence sound right. Its a sincere curiosity, not a poke.  And I hope they have given you better performance than stock.  Are they (valves and guides) of better material or such?

Am considering them for future project but its a K head.

Much better material MC. Nice thing is the intake valve is 34mm (same as the F2) and when you open the seat up to 90% of the intake valve OD you start moving some charge.

Thx. Got my current project to finish, then on to the "rat". "Moving more charge" sounds fun.

[simon#42]

i agree with mike about the quality , they are a very nice piece of kit indeed .  my logic for the improved guide wear was , although the stem is about 20% smaller they weigh 50% less so proportionately they should be better  . also as mike has already said the spring rates are around 30% less which should also be kinder on the cam and followers which cant hurt .

[MCRider]

i agree with mike about the quality , they are a very nice piece of kit indeed .  my logic for the improved guide wear was , although the stem is about 20% smaller they weigh 50% less so proportionately they should be better  . also as mike has already said the spring rates are around 30% less which should also be kinder on the cam and followers which cant hurt .

Ah good points.

But is the spring rate 30% less than stock or 30% less than HD would be otherwise?

I'm sold on the conversion, just looking for education.

[MRieck]

i agree with mike about the quality , they are a very nice piece of kit indeed .  my logic for the improved guide wear was , although the stem is about 20% smaller they weigh 50% less so proportionately they should be better  . also as mike has already said the spring rates are around 30% less which should also be kinder on the cam and followers which cant hurt .

What is interesting is Simon used the 5mm, 32mm intake valve on the exhaust side of the F2 to solve problems. I remember him posting something about, questioning if that is what he did and getting an affirmative answer. Well done on his part....a lucid solution.

[MRieck]

i agree with mike about the quality , they are a very nice piece of kit indeed .  my logic for the improved guide wear was , although the stem is about 20% smaller they weigh 50% less so proportionately they should be better  . also as mike has already said the spring rates are around 30% less which should also be kinder on the cam and followers which cant hurt .

Ah good points.

But is the spring rate 30% less than stock or 30% less than HD would be otherwise?

I'm sold on the conversion, just looking for education.

There you go MC. Anybody putting one of these kits in a stock cam bike is missing the boat.