Mo' Power....its time. 81GPZ1100

Now that I have the handling and braking under control, its time to put more go in the mill.

I'm torn between easy hot street and full tilt bozo on power.   I have to bore the cylinders due to the factory oval bore problem...uses a lot of oil.  It costs basically the same for one over as bigger bore kit.  Might as well go for close to 1200cc and bump the compression to 10.25.  I am looking for a bathtub head if anybody has one for sale or trade as well.  Otherwise I'll port and polish the head I have and go with a street race cam.  I live at 5500' on a hot summer day that's like 8000'...so you loose 2% per 1000 foot or 16% of your power..no amount of tuning regains this power its physics.  I need to get that back just to be at stock!  

Anybody have their magic formula that cam be shared for power?  IE: Cams used, bore, compression, port and polish tricks/guru's, experts worth spending money with etc....   Figure this can help out everybody else as well doing this.

Thanks
577nitro - JES

wrote:

I'm torn between easy hot street and full tilt bozo on power.   

 I live at 5500' on a hot summer day that's like 8000'...so you loose 2% per 1000 foot or 16% of your power..no amount of tuning regains this power its physics.
 

one vote here for full tilt Bozo power! practicality be damned!

to over come altitude you could go boosted.... kzrider.com/forum/13-bike-related/589368-81-gpz-1100-turbo

Yup. Go all in. It's not like you need it for daily commuting, right?

Even if you did, I went to school in SoCal with a guy who rode his blown KZ900 most days!

You might want to check with APE  kzzone.com/  
They have a lot of experience and sell package deals. 
Good luck and let the good times roll.

I don't know the seller but it looks like he has a few bathtub heads:

www.facebook.com/marketplace/item/175319...95-85d1-72e49940acda

I like this high-compression piston kit (1,135cc), over all others I've seen.  Change epay, to ebay in the link below:

www.epay.com/itm/292948393891?hash=item4...3:g:sHoAAOSwdGZcWVUe

 

wrote:

I don't know the seller but it looks like he has a few bathtub heads:

www.facebook.com/marketplace/item/175319...95-85d1-72e49940acda

I like this high-compression piston kit (1,135cc), over all others I've seen.  Change epay, to ebay in the link below:

www.epay.com/itm/292948393891?hash=item4...3:g:sHoAAOSwdGZcWVUe


 

Just post the correct link, doesn't matter if its not a live link, it can be copy and pasted into any browser, that link you posted is to a Chinese money payment site...., the links useless...

Thanks for the great info.   Probably do a kit for sure seems the best way to go.  Find another site, dynoman.com as well.

577Nitro

I am also building a 1197 street motor but the engine is out of a 1978 Police bike so I have a KZ head which I was told is perfectly fine to use for a street bike build. If you have a GPZ head you already have bigger valves in it than a KZ head so you should be OK with that head instead of looking for a bathtub head. Spend some money on cams, .410 lift should be plenty and get the head mildly ported so you don't loose too much bottom end.

I am using a 1015 block with modified GS1150 liners, with 76MM MTC 10.5:1 pistons.

Yeah I looking at the .410 from the kit.  I not sure what the advantage of the bath tube is other than maybe getting larger valves by going with a steeper angle. 
Somebody smarter than me can chime in...maybe better squish band. 

Having played around a lot with intake runner length on two strokes I know a longer intake tract helps low end mid-range be keeping the velocity up on the air-collum..same applies to four strokes as well.  So thinking is the 81 head is the one with the built in injector mount, so its pretty dang long and meaty low end,..not sure if that head can flow the carbs and cam. 

577nitro-

If you used a bathtub head you really need the pistons with crowns to match, especially with aftermarket pistons or modify the valve pockets to suit.
Chamber volume is the same at 40cc though so compression will stay the same.
I'd stick with a J type head as you will save a bunch of work and not really notice any difference.
 

How about complete bike already done 84 GPZ1100 1170, R&D Transmission, Pearson Crank, Larry Cavanaugh head, DYNO TUNED , Pogue DFI ?

 

I couldn't find the heads listed, I saw them last week, perhaps they have been sold...also my FB account is hosed up again.  If somebody still has this guys info I'd sure like to see if they are still around.

I'm not really sure if the 81 head is worth investing in.  With the goofy built in injector mount, it's unclear how that effects flow.    I once saw a description or info on the different type KZ/GPZ heads and their flow abilities from some race shop, however I have not been able to locate it again.   Ultimately my goal is a poor mans version of a  S1, minus the crank flipping and magneto's.  120HP at the wheel, at sea level correction would be plenty for me with this bike. 

From what I'm reading all of the larger cams require  clearancing (???), and the 81-2/J uses 17mm wrist pins, so there is a problem with using the bathtub heads (83/84) pistons due to them being 18mm?  Or is there a 17mm version of the twin swirel/BT head pistons for the 81/J model engine?  

Is the 83/84 crank a solid forged crank, or a pressed crank? 

So far I THINK this is the  formula I'm going to try, that I know will at least work.   Keep my 81' head (me doing the port and polish), .410 (or.383) cam, upgrade the valve springs per APE, Ti retainers, degree the cams, bore the cylinders over to square them 1138 or larger, at least 10.25 CR,  keep my Mic RS34 carbs, keep my 4into1 original Kerker, install my Dynatek 2000 ignition.  I'm hoping this is enough.   If it's not, then I'll search out a BT head.  What I found out from smarter people than me; the BT/TwinSwirl head makes more power manly due to larger valves and ports maybe also better squish/combustion(not sure about the last one). 

Still many questions floating around in my wee brain though!!!....

577nitro-

wrote:

wrote:

I don't know the seller but it looks like he has a few bathtub heads:

www.facebook.com/marketplace/item/175319...95-85d1-72e49940acda

I like this high-compression piston kit (1,135cc), over all others I've seen.  Change epay, to ebay in the link below:

www.epay.com/itm/292948393891?hash=item4...3:g:sHoAAOSwdGZcWVUe



 

Just post the correct link, doesn't matter if its not a live link, it can be copy and pasted into any browser, that link you posted is to a Chinese money payment site...., the links useless...