1982 GPz750 Phase II Making It more Unique.

Got it back together, kinda mixed results. It fires right up and wants to just jump right off the line. I took it for a cold 40 mile ride.

The first half of the ride was mostly on surface roads and it ran pretty damn well. So much so I had to blow through a red light since I lost track of my speed. Good thing it's Sunday.

Once I hit the freeway it all went to shit. It accelerated great until I got over 70 and 6k revs and then everything goes completely flat. You have to be WOT in 5th to maintain speed and shift down to get anything else out of it.

Back to checking everything. :S

Nice work on the tail light, there were mod kits available back in the day to recess the rear light as Baldy has done too. If any of the 'comittee' beat you upover that tell them it is a 'period mod '

It accelerated great until I got over 70 and 6k revs and then everything goes completely flat.



The 115 jets sound a bit small, I'm running 137.5 on mine, another member here recently went to a similar big size. with a 4-1 on pods.
It sounds too big I know, but feed the cat.

Maybe lift / shim the needles for a better or worse feel...really that kerker will probably require some upjetting. At 6k this is when main jets fully kick in and it enters warp mode.

My Lawson sounded so evil when it hit main jets, ripping my arms out of their sockets. definitely the stupidest bike I ever had.
pure heavy metal. :laugh:

The "committee" eh. Like I say, if it's done well, it will get the respect it deserves. :whistle:
Steve

But I'm on the 'committee' here too, so the joke is on me too :

Nothing wrong with being a bit opinionated here, you can't be passionate about these without your own take on how they 'should' be.

Only today a guy enquired about buying a super rare GPz550 fairing and mounts currently on ebay for a £100.
It was for a GT550 so I told him he could only have it if he doesn't drill it as it is far too precious lol . How unreasonable of me :laugh:

Tyrell Corp wrote: Nice work on the tail light, there were mod kits available back in the day to recess the rear light as Baldy has done too. If any of the 'comittee' beat you upover that tell them it is a 'period mod '

Thanks I'm really liking it and the blinkers are pleasing me as well, much better than the Chinese crap that was on there. I guess that's 2 votes for and at least 1 grumble... I'm not sure if he approves or not, he seemed to be on board with the headlight this is pretty much along the vein. I now have to find something for the front blinkers.

Tyrell Corp wrote: The 115 jets sound a bit small, I'm running 137.5 on mine, another member here recently went to a similar big size. with a 4-1 on pods.
It sounds too big I know, but feed the cat.

Maybe lift / shim the needles for a better or worse feel...really that kerker will probably require some upjetting. At 6k this is when main jets fully kick in and it enters warp mode.

Really?? It had 110s before and now it seems worse. I've had this problem to a small, intermittent degree, since I've had it running. Even with the original leaky headers and mufflers. I'm sure altitude is a factor the ride yesterday ranged from 4000-5000 ft without going up the canyons, too cold and risky running across an ice patch. I'll raise the needles and see if it gets better or worse. Then look into up-sizing the jets if prudent.

Speaking of the Kerker, I've been meaning to post a pic specifically for you. I've dragged it at least 3 times and has the scars to prove it. I know there was that risk but I've been having more fun than I thought I would have. I have to find a way to get it slightly outboard, to the rear and angled up. I'm not sure how to do this except to maybe take it to a exhaust shop and have them bend or weld me something since there is no way I'm going to find just the pipe between the collector and the can.

I never liked the square tail light. In the 80's everything was L7.
Steve

swest wrote: I never liked the square tail light. In the 80's everything was L7.
Steve

So that's 3 in the YES column.

Who gives a SHT what others think as long as you like it. :whistle:
Steve

Tyrell Corp wrote: The 115 jets sound a bit small, I'm running 137.5 on mine, another member here recently went to a similar big size. with a 4-1 on pods. It sounds too big I know, but feed the cat.

At 6k this is when main It had 110s before and now it seems worse. I've had this problem to a small, intermittent degree, since I've had it running. Even with the original leaky headers and mufflers. I'm sure altitude is a factor the ride yesterday ranged from 4000-5000 ft without going up the canyons, too cold and risky running across an ice patch. I'll raise the needles and see if it gets better or worse. Then look into up-sizing the jets if prudent.
.

What should the stock jet sizes be? With the altitude here in Utah, the stock settings would most likely be verging on too rich already, other than a lot of early 80's bikes were jetted so lean for emissions legislation. I don't know if you've ever had them set to stock settings, but I'd go back to those if you can, see where you are at and then work from there changing one thing at a time. I have a V&H on my KZ650 otherwise it's pretty much stock and it runs perfectly on the stock jet sizes here in UT at altitude. It looks from the pictures that you are still running the stock airbox, so you shouldn't need huge changes just for an exhaust and like I said the altitude might be enough to already compensate for that. What do your plugs look like are you sure the bogging at high rpm is not too much fuel, try pulling the choke on a little when it's doing it and see if that makes it better or worse, that way you will know if you are too weak or too rich.

swest wrote: Who gives a SHT what others think as long as you like it. :whistle:
Steve

I know, It is nice to know if it something is way off base. You definitely know what I mean.

I besides the jacked rear blinker mounts I'm leaving everything alone/reversible. I'd like to reuse other bike parts like I've done for the taillight and blinkers ('07 ZR7) and headlight ('82 Spectre}. I'm trying to keep the aftermarket parts to a minimum, at least use used parts like the fender delete kit. Even then i made use aof the left over 20 gauge SS sheet to make the mounts for my green coils.





This just before I tucked up everything ran a wire from 2-3 trigger contact to the tach wire and put everything back.

redhawk4 wrote:
What should the stock jet sizes be? With the altitude here in Utah, the stock settings would most likely be verging on too rich already, other than a lot of early 80's bikes were jetted so lean for emissions legislation. I don't know if you've ever had them set to stock settings, but I'd go back to those if you can, see where you are at and then work from there changing one thing at a time. I have a V&H on my KZ650 otherwise it's pretty much stock and it runs perfectly on the stock jet sizes here in UT at altitude. It looks from the pictures that you are still running the stock airbox, so you shouldn't need huge changes just for an exhaust and like I said the altitude might be enough to already compensate for that. What do your plugs look like are you sure the bogging at high rpm is not too much fuel, try pulling the choke on a little when it's doing it and see if that makes it better or worse, that way you will know if you are too weak or too rich.

That what I was thinking. The stock size is 110 which is what was in there. I wasn't sure how much the pipes and muffler would affect the mixture so I took a blind stab and up jetted. The rebuild kits came with 2 sets of jets 110 and 115 so I swapped them over. I didn't think to open the enriching circuit until I got home. it was so cold I didn't want to go back out. I'll play with the needles a bit, up and down, and see what happens next time it warms up some.

Redhawk, the (avatar) bike is running on pods and a 4-1, it runs really nice from off idle past the redline, plugs look ok and fuel consumption about what I expect 45 mpg maybe. It has an 'air corrector kit' and the needles are different too. I bought the bike like that and it runs so nice I haven't changed anything. ( I suspectthe PO may have had quite a bit of trial and error to get there.

The conventional wisdom of going up two main jets sizes as a starting point seems way off on these, a couple of other 750R owners here are using similar sizes. A carb specialist recommended going even bigger. Odd I know, a couple of sizes up usually works for the 550's...but it works really nice.