For a strictly street ridden bike like I think you want to keep...I'd just freshen the head with a valve job, springs, etc. with a clean up on the ports...matching the manifolds to the head and cleaning up the casting rough areas...like you said ...a very basic port/freshen up job. I'd keep the stock cam tensioner also. Bore it to 1015 so the liners are left with more meat and you would still have an overbore left if something bad were to ever happen. Just the new hone and rings with the added compression would make the bike feel much stronger. For what you are doing, the crank wouldn't need to be welded or the trans gears cut. Welding the crank would be a good idea to do if the finances are good as would the trans cut but really not necessary for what you would end up with. That would save money for other areas. A set of 28's would wake up the bike for a lot less then those 29's although you already have them. Either way would be improvement. As for cams, a set of Web turbo cams with .340 lift would be great. A little more lift but without much duration would give you bottom end and some mid-range power where you actually use the bike most. J model cams are bigger then stock Z or KZ cams and would help but certain J models don't have cable tach drive so would want to find a pair from a motor in a Spector...I think...that used a cable-driven tach.Some of the earlier models of the J series used a cable-driven tach so you'd have to find one of those. Maybe even cams from a 83-84 GPZ. You'd lose the cable tach though. I wouldn't go much over those as they use more duration to move power curve up in the rpm range.Basically a good fresh motor with a few tweaks to boost power but not take away any of the user-friendly rideability you now have. You have that 1105 to put the bigger parts in to have your fun with...but what Dr. Gamma said in his post would be a fantastic Z with more power if you were going to get more serious with the build...
1980 LTD (changed over the years), 1979 LTD (being rebuilt), 1977 KZ turbo and various KZ's in various states of build. KLX110
i would do the 1015 overbore to gain from the fresh bores,forged pistons and compression bump.
while NOT having to source a 1000 cylinder.
i am betting all mods being the same with bore being the only difference you can't tell (seat of the pants) a 1015 from a 1075 .
and by just going 1015 you can still have a rebuild left to go to 1045 in your stock cylinders.
i raced two strokes for years do all my own boring and honing and hate to bore a cylinder any more than is absolutely necessary.
exhaust,compression,carbs,cams and headwork will make way more difference than a few cc's.
thats my .02 fwiw,
I agree with this too unless your interested in taking it to the next level by swapping in gpz 1100 stuff.
Thanks for the help guys! I plan on sticking with my 903 block and I'm very likely boring it to 1015 [still working out prices - new pistons are the most expensive part of the rebuild and are not necessary, just a performance boost]. If so, I'm using my 29mm smoothies and I'm trying to find a set of GPz 1100 cams and will get a street or "stage 1" porting job. I'm talking to Pit Stop Performance and Larry C. [there's a 6 month lead time at Redline and I unfortunately cannot wait that long without a motorcycle].
This isn't a hot rod build - I ride this bike every day (it's been 26 and 25 degrees the last two mornings I rode to work, respectively) and I don't want any issues. I have an ex-AMA Superbike engine that's been bored to 1105 which is my hot rod engine. I like the fact that I'll have the chance to bore 1045 in the future, if needed - but I'd likely just get a new 903 or 1015 block if necessary.
New valve guides, new cam chain, rollers, and tensioner [maybe], new stainless steel valves and springs, and a 3-angle valve job.
Do I need to replace the studs with APE studs and nuts? My currents nuts are a little rusty [hehe] so I wouldn't mind replacing them on a strictly cosmetic basis.
And do I need to undercut the transmission and weld the crank? Yes it'd be nice, of course. But do I really NEED to? I certainly won't be reving it to 6k then dropping the clutch.
Thanks racer! I already have a set of 29's, so that is taken care of. I'm considering the GPz cams - the do not have a tach gear? That's pretty damn important to me - especially as a stock appearing digital tachometer is something like $200 the last time I checked - for that stuff combined, I may as well buy a set of new Web's!
Do you, or anyone else on here, have experience with Web 118's?
Now I'm looking at finding a 1015 block and boring it to 1075... Either way (903 > 1015 or 1015 > 1075) I'll be getting the cylinders bead-blasted and bored so it's a 6 to 1/2 dozen scenario isn't it???
Time to get my KZ fixed up. Just gonna do the valve guides and seals while I save up for a proper rebuild.
To pull the head off, does the engine need to be out of the frame? Do I need to cut the cam chain or can I slip the cams out carefully with the slack in the chain? Anything else special I need to be aware of?
No need to take it out of the frame nor cut the cam chain.
There are some factory videos on here which are professional with more information then just disassembly compared to mine. But I go over some of the real world issues that you may run into like stuck cam caps, head or jugs. It may be to replace any worn chain guides. Pay close attention to the front chain guide which is held in by a screw in the front of the cylinder block. Good luck.