Got a dot head for my 1100N

[Panos]

Camshaft swap was the reason i got the dot head and also i thought the dot head flowed better than the shim head . Another reason was the shim spitting at high rpm and easier valve adjustment .

As far as i have looked i couldn't find any replacement cams for the shim head .

Now i am thinking of three options

1 Get the M head converted to screw adjustment (PITA) ,do bigger inlets and porting . This way bst 40 and airbox will fit for sure and the M head (which i already have) gets used .

2 Get a forked head bandit or gsxr 1100 ,do bigger inlets and porting . Probably the  rubbers of M head for BST40  match the ports and they are not way off like the dot head and airbox can be used  , i hope port heights are the same are they though?

3 Just fit bigger inlets , port the M head and have the cams reprofiled in uk , thats the more sensible option  .

I am itching for option 1 unless option 2 a bandit head can perform the same and port heights match .

[Gsxrsam]

Mine has standard cams, bandit pistons, mild porting and a mild skim, some fcr 39s and dyno said 150 ish horses.....

 

[Fazz711]

Could convert to shim under bucket.

Spitting shims seems to be one of those things people worry about bit never actually experience.

I don't know of anyone who it has happened to but suppose it could happen 

[Gsxrsam]

if you are revving a gsxr 11m/n motor to the point of shims coming out, there was something wrong with it the first place..

 

[DAZ]

12 minutes ago, Gsxrsam said:

if you are revving a gsxr 11m/n motor to the point of shims coming out, there was something wrong with it the first place..

 

Is it one of those "myths" that grew on the internet ?, maybe back in the day from production racers ,even from the 750m which obviously rev higher or the early gsx600f which also had shims for the first year of two I believe, like when Whitham was racing them. 

[DAZ]

8 hours ago, Fazz711 said:

Could convert to shim under bucket.

Spitting shims seems to be one of those things people worry about bit never actually experience.

I don't know of anyone who it has happened to but suppose it could happen 

Meant to add to above post 

Edited August 3, 2023 by DAZ
Fat fingers

[Gixer1460]

10 hours ago, Fazz711 said:

Could convert to shim under bucket.

Spitting shims seems to be one of those things people worry about bit never actually experience.

I don't know of anyone who it has happened to but suppose it could happen 

These don't use 'buckets' - that conversion would be far more engineering than just changing to trad tappets. As said spitting shims is a urban street myth mainly only experienced by racers who don't know what rev limits are! Don't buzz the engine and you won't spit shims! With 1100's the power is on the slide after 10.5k generally so trying to rev to 12k is utterly pointless!

[Panos]

Well that makes sense now , never thought these stories were about 750's or 600's .

Found and read again the article below and there is  no mention of cc's .

[DAZ]

Having read the article you posted I have to ask : 

if they built an 1186 motor specifically to drag race why would they not set the valve springs pressure to suit the expected rpm limits of the motor,to ensure it didn't float the valves ?

why didn't it have a rev limiter set so it didn't over rev , soft cut limiter aren't new 

if you haven't read @Oilyspannermy route to oily happiness thread in projects his 1216 M sounds close to what you want and maybe worth the time to read it you haven't already seen it 

 

 

Edited August 3, 2023 by DAZ

[Panos]

1 hour ago, DAZ said:

Having read the article you posted I have to ask : 

if they built an 1186 motor specifically to drag race why would they not set the valve springs pressure to suit the expected rpm limits of the motor,to ensure it didn't float the valves ?

why didn't it have a rev limiter set so it didn't over rev , soft cut limiter aren't new 

if you haven't read @Oilyspannermy route to oily happiness thread in projects his 1216 M sounds close to what you want and maybe worth the time to read it you haven't already seen it 

 

 

I think the article promoting the shim fix was separate from the text above it , i could be wrong though . Most motorcycle magazines are just promoters anyway .

Not only have i read @Oilyspannerthread , i have gone through it many times and also kept notes !

And of course the evo bike thread of johnybump , i will copy as much as i can from them .

Both awesome projects and goldmine of knowledge

When i grow up i wanna be just like them !

[Gixer1460]

5 hours ago, DAZ said:

Having read the article you posted I have to ask : 

if they built an 1186 motor specifically to drag race why would they not set the valve springs pressure to suit the expected rpm limits of the motor,to ensure it didn't float the valves ?

why didn't it have a rev limiter set so it didn't over rev , soft cut limiter aren't new 

I see the 'spitting fix' is mentioned and seems to have taken the normal shims and made them into 'Lash Caps'. These were popular with big V8 engines mainly to stop the valve heads getting mushroomed when using stupidly high spring poundages! I would imagine making up loads of modified 'shims' to account for different clearances would be a PITA but a deeper retainer well / taller shim is definately a 'fix'.

Rev limiters and especially 'soft cut' limiters are somewhat pointless when you leave the line essentially at peak rpm and then make 4 additional gear changes within a 9 - 10 second pass. You shift based on reaction to the shift light (if you have one) which will be flashing like a christmas tree so missed shifts are enevitable. When more 'robust' valve actuation methods were available, a shim head isn't maybe the best choice for a drag race engine. I used a 1100M head (unmodified shims) with NOS for drag racing and never had a problem - just sayin'

[Gsxrsam]

Using the 750 cdi on the 1100 was the tried and tested way to destroy the motor......

[Baron]

What is the reasonable rev limiter for 1100 shim head to prevent spitting? Stock is 10,500 if im not mistaken.

[Upshotknothole]

Well, considering my GSXR 750 is a shim head and the rev limiter on it is 12.5K, and I've hit it plenty of times without spitting a shim, I would imagine that whatever the stock rev limit is for the 1127s is more than safe. I've also got an 1127 shim head with RS38s that's pretty rev happy and I'm sure I've hit the rev limiter on it plenty of times as well. Really sounds like all of the shim spitting was done on poorly set up drag bikes that had nothing to do with real world riding.

Still wish I could get aftermarket cams for my shim heads.

[Duckndive]

2 hours ago, Gixer1460 said:

 but a deeper retainer well / taller shim is definitely a 'fix'.

Ape used to sell just such a fix 

[DAZ]

Just musing this shim spitting (or not) issue , i was wondering if engines fitted with "uprated" cams are the ones that are prone to losing a shim maybe because of more aggressive (faster) opening and closing ramps causing a loss of contact between follower and shim ?

[Upshotknothole]

9 minutes ago, DAZ said:

Just musing this shim spitting (or not) issue , i was wondering if engines fitted with "uprated" cams are the ones that are prone to losing a shim maybe because of more aggressive (faster) opening and closing ramps causing a loss of contact between follower and shim ?

Without reading any of the articles, just based on my personal experience destroying engines. Hot cams with stock valve springs, and high RPM are a good way to float a valve, and with these shim heads, spit the shim out.

Edited August 3, 2023 by Upshotknothole
more info

[slayer61]

This is, no doubt, the very reason that Megacycle don't make cams for these bikes... due to their fragile valve train.

 

Quote

We do not offer camshafts or valve springs for 1991-92 models. Due to the fragile valve train design, we do not recommend installing high performance cams in these models. It is possible to convert to 1989-90 style cams, rocker arms, etc. The charge is $100.00 per cam to weld and machine the thrust flange on 1989-90 cams to be used in the 1991-92 cylinder heads.

 

[jonny1bump]

Got more chance snapping crank first.

[Upshotknothole]

2 minutes ago, slayer61 said:

This is, no doubt, the very reason that Megacycle don't make cams for these bikes... due to their fragile valve train.

 

 

You used to be able to get cams for these heads. More likely the fact that they didn't make that many. Rest of the world got shim head 750s for only 2 years, we got them in the states for 3. The 1127s weren't made with them for very long either. Yet the tappet heads were made from 85-2007 with the bandits and Fs. No one wants to make cams for a 30 year old bike that was only made for about 2 years when they can sell you a conversion kit to run cams for an engine that was made for 22 years.

[jonny1bump]

Yep need correct spring pressure, I did my conversion for more choice of cams and easy valve adjustment, but it involves welding cam face and re machine, heads were more readily available then, not sure id do it now days.

Ray always said to me when I was playing on tracks its serviceable item be prepared to replace.

Edited August 3, 2023 by jonny1bump

[Dezza]

Is there an option 4: shim head 750 cams in a shim 1100 head?

[Gixer1460]

24 minutes ago, Dezza said:

Is there an option 4: shim head 750 cams in a shim 1100 head?

Are they any different?

[DAZ]

19 minutes ago, Dezza said:

Is there an option 4: shim head 750 cams in a shim 1100 head?

Do long stroke 600/750 cams fit the 1100 heads ?* Are the cams noticeably "hotter" ? Is it possible to run an intake cam on the exhaust as happens on the gsxr1000s ? Is it worthwhile ?

* The short stroke 750 ones I know will fit 11/1200 tappet heads.

[Panos]

29 minutes ago, Gixer1460 said:

Are they any different?

I remember reading in the vault that the valve spacing is different so they can't be interchanged .