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Mechanics 101 Can't get it to run right? Find a trick to add HP?
From the first oil change to completely rebuilding the engine,
this is the place to talk about the heart of the beast!


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Old 03-14-2018, 05:39 PM   #11
Lachie
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Quote:
Originally Posted by Dhawk12 View Post
Just wanting to double check what would make replacing the rocker arms necessary. There is no pitting or score marks on them, just places where the surface is not completely flat (ie a low spot where it appears the rocker arm is not touching the surface of the cam lobe) These low spots only take up at most a strip about 1/8" on the worst one.

Also, I know the camshafts from a 90 GSXR 750 would fit, does that mean that the head is the same? Or at the very least are the rocker arms the same?
As for swap ability
follow this to see guide at Katanawiki I haven't researched if a 90 head would fit on your bike possibly yes but absolutely no idea for sure.I think the cylinder size is bigger on your short stroke so this would overlap the combustion chamber really thats just a guess ATM

http://katriders.com/wiki/index.php?...ross_Reference

Your rockers should look something like this


left insert pic shows slight curve over the face
Main pic shows contact area were the cam lobe rotates over the face of the rocker. There is a slightest of lines through the middle indicating highest contact point/patch but no appreciable wear should be there

The rocker and cam will wear which is why you need to adjust them if your rocker is showing signs of abnormal wear and you cant adjust to the limits then they would need to be replaced.

if there was significant depression on the face along that line then yes replacement would be advisable if not for the simple point of how long it would last even if you could adjust it not to mention is probably putting stress on the cam lobe and valve train.

My opinion but someone else may chime in

Last edited by Lachie; 03-14-2018 at 06:09 PM..
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Old 03-14-2018, 06:55 PM   #12
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Ya, I looked on partzilla and most of the parts for the valvetrain are the same between the pre-kat 750 head and the 88-90 gsxr 750. The head itself has a different part number but I have seen in other threads that the head is the same with different paint, etc.

The strip I am referring to on my the rocker arms goes the other way if that makes sense. In your picture's orientation it is vertical, whereas the line in your photo is horizontal. I should have taken a picture before I tucked everything away, but I didn't and I don't want to look at it again today lol.

Anyways, I ended up buying an entire 90 GSXR head with cams, rockers and bearing caps as it seemed to be the most cost efficient solution, although one way or the other, ill be left with a spare head, valves, etc.

Now I just need to figure out the quickest and smartest way to get the bike up and running again when I get it. Either I just bolt the GSXR head onto my engine, meaning I will have to fork out another $70 for a head gasket, or I take the rockers out of the gsxr head and just follow 92junker's advice above that I shouldn't worry too much about mixing and matching cams and bearing/cam cap surfaces.
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Old 03-15-2018, 01:23 AM   #13
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Not sure if the head will fit. Some of the gsxrs had long/short throw opposite of what the Kat's have. There's an article in the wiki that goes into a decent bit of detail on pretty much this topic. (Engine parts compatibility)
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Old 03-15-2018, 03:03 AM   #14
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There may be other things like inlet port centers etc etc that may not be quite the same, I have heard the dot head has a steeper inlet angle stuff like that, so carbs might not fit quite the same

You would want to check valve to piston clearance etc , it's quite conservative on the 89 but that may change with the different head even though the cam might have a little less lift compared to GSXR 89 spec still bigger than the Kat, duration may also be different as would the valve angle (maybe).

Another thing is the valve cover may not fit properly the pre to post Kat covers are slightly different Pretty sure you can't put a pre cover on a post due to the cam follower height but with the roller chain on the 90 probably can. The cam tensioner tunnel on the post is shorter (sticks out less) from the block than a Pre kat engine even though they are similar there is still lots of differences between engines

Just swapping the cams will be good but reduced size valves ???? don't know how that would go I would be thinking you might actually be losing some performance even if marginally.

All this stuff you will need to check but the only way is to try and see.

For my money I would be rebuilding the 89 head all the journal diameters are the same rocker and cam and yeah you don't need to take the head off either so would be quicker easier all you have to do is make sure all the arrows are pointing in the right directions

Last edited by Lachie; 03-15-2018 at 03:51 AM..
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Old 03-15-2018, 08:42 AM   #15
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To All your concerns. The Kat motor is based off the early GSXR. The only thing you need to check is the cam lobe count. The valve trane changed between the years. The wiki has all the info on the cam swap. If you can find a Dot head buy it, Iíll take one.
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Old 03-15-2018, 06:39 PM   #16
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Quote:
Originally Posted by shpielers View Post
Not sure if the head will fit. Some of the gsxrs had long/short throw opposite of what the Kat's have. There's an article in the wiki that goes into a decent bit of detail on pretty much this topic. (Engine parts compatibility)
Ya it looks like the 90 gsxr head is long stroke, so not a direct fit for the head itself, whereas the 88-89 head is a direct fit onto pre-kats. That is according to this wiki anyways.

http://katriders.com/wiki/index.php?...ross_Reference

SO looks like I'll get to save $70 for a head gasket and just swap the cams and rocker arms over. There shouldn't be any issue using the bearing caps from the gsxr head should there?

Anyone want to buy a 90 GSXR 750 head without rocker arms or camshafts lol?

Quote:
Originally Posted by 92xjunker View Post
To All your concerns. The Kat motor is based off the early GSXR. The only thing you need to check is the cam lobe count. The valve trane changed between the years. The wiki has all the info on the cam swap. If you can find a Dot head buy it, Iíll take one.
There is a bunch of the pre-kat 750 heads on ebay that I found in my journey for camshafts (I believe the pre-kat heads are all dot right?)

https://www.ebay.com/b/Motorcycle-Cy...70/bn_51195303

This one is only $70 USD

https://www.ebay.com/itm/89-97-Suzuk...AAAOSwzRlaSt3a

Last edited by Dhawk12; 03-15-2018 at 06:39 PM.. Reason: Automerged Doublepost
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Old 03-15-2018, 09:42 PM   #17
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Quote:
Originally Posted by Dhawk12 View Post
Ya it looks like the 90 gsxr head is long stroke, so not a direct fit for the head itself, whereas the 88-89 head is a direct fit onto pre-kats. That is according to this wiki anyways.

http://katriders.com/wiki/index.php?...ross_Reference

SO looks like I'll get to save $70 for a head gasket and just swap the cams and rocker arms over. There shouldn't be any issue using the bearing caps from the gsxr head should there?

Anyone want to buy a 90 GSXR 750 head without rocker arms or camshafts lol?



There is a bunch of the pre-kat 750 heads on ebay that I found in my journey for camshafts (I believe the pre-kat heads are all dot right?)

https://www.ebay.com/b/Motorcycle-Cy...70/bn_51195303

This one is only $70 USD

https://www.ebay.com/itm/89-97-Suzuk...AAAOSwzRlaSt3a
Nope....early slingshot heads, will literally have a dot on them.
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Old 03-15-2018, 10:06 PM   #18
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Yea, but it is my understanding from reading the wiki and other forums, that the pre-kat 750 head is the same as the early slingshot 750 gsxr head (88-89), is it not? And I can confirm that my 1989 Katana 750 has a dot on the head, as does my 1997 Katana 750.

This is what I can find on other forums:

"Suzuki also used the dot head on some of the GSXF750 'Teapot' models (Katana - to you boys across the pond). It's exactly the same as the GSXR 750 J or K from '88 & '89 with the same small combustion chambers and 1100 size valves , but the cams were a lot milder , and the GSXF pistons were lower compression than the GSXR."

http://www.gixxer.com/forums/15-oil-...-dot-head.html

And I found this in a camshaft replacement forum here:

"Since were on the topic of cams/top end and the such I have done alot of research on the oil cooled cylinders heads as of late. PRE 98 KATANA 750'S HAVE THE BIG VALVE SLINGSHOT HEAD!!!!!! This is the best head in existance for oil cooleds and only come on the pre 98 katana 750's and slingshot (88-89 gsxr) 750's. They have 28.5/25 mm big valves and small combustion chambers and the katana head IS the same as the slingshots only with VERY mild cams. I have personally verified this buy measuring both set-ups in valve dia. and cc'ing the heads. ALL parts in the valvetrain are the same verified by cross referencing the part #'s. If any of you have switched your pre 98 750 heads for any other gsxr head besides the slingshots you have screwed yourself (or switched to the slingshot's you swaped out to the same head). It is a very popular misconception (one that I believed and many others as well) that the katana head is different. IT'S NOT!!!! Keep your katana head I'll post the other stuff when I go to work..."

http://katriders.com/vb/showthread.p...ft+replacement

Last edited by Dhawk12; 03-15-2018 at 10:35 PM..
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Old 03-19-2018, 01:22 AM   #19
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One thing I found when doing swaps is that not all times do you get all the info or something is just a bit different on yours to everyone else (or something Like that) point was unless it's a known swap you may run into lots of stuff that not quite right
case in point the 90 head on a pre. (yep I know your not going to do now) I would imagine the 90 head would be more similar to the post head than the pre but have no idea really.

Anyhow, just for shits and giggles I lined up a pre and post 750 head to play spot the difference

obvious differences are
Cam tensioner tunnels are markedly different



And inlet angle is also (this is the problem / challenge when mounting DOT heads on GSXR's as they have to mod the fuel tap)



Casting internally is quite different with different baffle/strengthening plates, valves look to be longer too well at least spring length looks longer
So just trying to point out all the things which could potentially be a challenge with any swap. Different part numbers aren't just all about color

Yeah they are all based on the same design but very different when push comes to shove. Anythings possible though just depends on how many challenges need sorting and how much research you need to do to overcome it
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