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Time to rebuild my old GPz

Work in Progress

Moderators: chrisu, paul doran, Taffus, KeithZ1R

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Kwackman
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Re: Time to rebuild my old GPz

#16 PostAuthor: Kwackman » Sat Mar 10, 2018 12:59 pm

chrisw1 wrote:I think I would use the standard swing arm ....... that one looks a bit too bulky for my eye

Agreed.
Also, the braced one looks taller where the chain goes over it at the front?
It's hard to tell from the photo though, so could be a red herring!
Good luck anyway, I'm watching this thread with interest!
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Re: Time to rebuild my old GPz

#17 PostAuthor: Philippe » Sat Mar 10, 2018 5:30 pm

Hi GPZ592

the alloy swing arm looks way too heavy to be ment for a GPZ550.
Try to replace the bushings or bearings from the original swingarm with new ones, I think that will be an improvement.
Replacing original parts with aftermarket parts seems tricky to me if you're not sure if those parts were designed for that specific bike. I think you need a lot of experience and better tools than a disc grinder to keep it safe to ride on the road. Don't forget that an insurance company does no charity in case of a severe accident.
No offence ment! Keep it safe!
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GPZ592
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Re: Time to rebuild my old GPz

#18 PostAuthor: GPZ592 » Sat Mar 10, 2018 9:33 pm

I think I would use the standard swing arm ....... that one looks a bit too bulky for my eye

Agreed.

Chris/Kwakman - if I'm honest I had my reservations as well. I think it's the under bracing is just overkill for a 550. it would probably look great on a physically bigger bike like a 1000 or 1100.

No offence ment! Keep it safe!

None taken, Philippe. Part of the reason for this thread is to get feedback and ideas from other people.

Anyway, I thought I'd try to get a feel for how it would look and managed to temporarily work around the clearance issues, but then run into the next problem. The top shock rocker would not line up to the frame mount. It took me some time to fathom out what was going on, but I figured it out when I compared the 2 swingarms. Look at the previous picture of the 2 arms side by side. You can see that the lower shock mount is formed by 2 plates bolted onto the lower side of the swingarm. the ally one uses the standard plates, but because the main beam of the arm is deeper, they are lower by about 15mm so it pulls the shock down and alters the angle of the top rocker arm. Remember what I said about this looking like it wasn't built around a bike - I reckon someone has taken the dimensions of a standard arm without reference to the frame. How else would you get all these problems ?

Here it is, temporarily fitted

IMAG0320.jpg


I did check the chain run with a piece of ally on the sprockets to see if it would clear and it would, but I did use a 17t (+1) front sprocket. However, thats a moot point now.............

IMAG0323.jpg

IMAG0321.jpg



So if I really wanted to use it, I would get the under brace removed, then I'd need to make up new lower shock plates, then remove part of the footrest mounting, which in turn means changing footrest mounts, etc, etc. It's a shame because an ally arm was part of the look I was going for on the completed bike. Never mind - maybe, I'll just spray the standard arm in ally paint :shock:

So now it's time for plan "B" :D
"Racing is life. Anything before or after is just waiting" - Steve McQueen

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Re: Time to rebuild my old GPz

#19 PostAuthor: Philippe » Mon Mar 12, 2018 4:22 pm

Hi
go for plan B! Paint the original swingarm in an ally color so you won't change the wheelbase nor the ground clearance of the bike and with new bushings and/or bearings the steering capacity of the bike doesn't get worse anyway. You allways have to wait and see when you change the original swingarm with one of another bike.
Good luck
Philippe
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GPZ592
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Re: Time to rebuild my old GPz

#20 PostAuthor: GPZ592 » Thu Apr 19, 2018 1:47 pm

So, It's been a few weeks since my last post and progress has been slow :(

I did re-visit the ally swingarm and spoke to couple of people about modifying it, but their considered opinion is there is too much that needs changing to make it viable. Oh, well - it's headed for ebay, hopefully someone can use it and I'll get something back into the kitty :D

So, I looked at plan "B" and re-fitted the original swingarm. Whilst it wasn't too bad, it just looked a little flimsy against the new wheels/forks -

IMAG0326.jpg


So I started to experiment with the possibility of getting an extra piece welded onto the bottom of the main arm to beef it up a bit. Using a cardboard template & duct tape, I reckoned a 1/2" "U" channel welded onto the bottom will achieve the desired effect -

IMAG0333.jpg


The other thing I noticed was that by being black it "disappeared" into the frame. That's to say you didn't notice it as it was the same colour as the frame. Maybe I'll spray the swingarm black instead of ally - that might work, but I'll see what the arm looks like once modified.

So the frame/forks/wheel & swingarm are now away being modified to suit.

The electrics have also gone away for refurbishment, so it's time to look at the engine. Once again I have some modifications planned and I'll update as things progress. :)
"Racing is life. Anything before or after is just waiting" - Steve McQueen

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Re: Time to rebuild my old GPz

#21 PostAuthor: GPZ592 » Tue Apr 24, 2018 8:26 pm

The first modification I wanted to do on the engine, was to replace the "H" GPz ignition plate & bob weight for the advance retard, with the later "A" series static pickup plate & CDI box. The newer CDi has the advance curve built in and also has a rev limiter, which the standard "H" ignition doesn't. I've done this successfully on the GPz750 motor in my P&M and that was a straight swap - not so with the 550 ! When trying to fit the later pickup plate it was fouling on the webs used for the original plate.

Original "H" series plate

IMAG0257.jpg


Newer "A" series plate fouling on the crankcase web

IMAG0267.jpg


As it happens, I had a set of the later "A" 550 crankcases and I could see the casting for the pickup plate was different - the lower left support had less of a web on it.

"H" cases

IMAG0266.jpg


"A" cases

IMAG0265.jpg


So, a good mate took them to work and using a 90 degree drill, took away part of the casting. They came back like this

IMAG0455.jpg


Ignition plate now sits true :-)

IMAG0458.jpg


I'll have to get the loom modified to accept the newer "A" series CDI and find somewhere to mount it as it's larger than the standard "H" item, but I like the fact it has the advance curve & a rev limiter built in. :D
"Racing is life. Anything before or after is just waiting" - Steve McQueen

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Re: Time to rebuild my old GPz

#22 PostAuthor: GPZ592 » Fri Dec 07, 2018 8:32 pm

Well, its been nearly 8 months since my last post and I'd like to say there's been lots of progress, but.................................

I won't bore everyone with the obvious excuses about balancing work, family & garage time but a combination of the former 2 limited the latter. oh and actually riding my other bikes in the summer - although my KH400 expired and needed some TLC and that's still not back together yet :( You may see a pattern forming here.................

Anyway, it's not all bad news. I have been trying to keep thing ticking over in the background and some progress has been made, so I'll post some updates and try and get this thread back up to the present :)
"Racing is life. Anything before or after is just waiting" - Steve McQueen

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Re: Time to rebuild my old GPz

#23 PostAuthor: GPZ592 » Fri Dec 07, 2018 8:53 pm

So lets start with the electrics.

As I'd already said, there were corroded terminals, damaged/hardened cables, repairs and it's a 35 year old loom. I could have had it repaired, but I've suffered too many strange issues with dodgy electrics, so I commissioned a new loom and all switches/senders,etc were stripped, checked and cables replaced to give them a clean bill of health.

Old Loom

IMAG0244.jpg


New Loom

IMAG3759.jpg


I've also stripped and cleaned the clocks as they were looking tatty. The worst part of this was removing the inner strip that holds in the clear plastic face panel. Some judicious use of a small screwdriver persuaded it to part company so I could clean it thoroughly. Reassembly wasn't too bad, just fiddly. I didn't zero the milage as I want to keep the history of the bike intact where I can.

Before

IMAG0199.jpg


Face plate off and the internals don't look at all bad

IMAG0203.jpg


35 years of grime....

IMAG0206.jpg


Teasing off the cover

IMAG0207.jpg


All stripped

IMAG0210.jpg


All reassembled and looking good

IMAG3757.jpg
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Last edited by GPZ592 on Mon Jun 01, 2020 11:44 am, edited 2 times in total.
"Racing is life. Anything before or after is just waiting" - Steve McQueen

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Re: Time to rebuild my old GPz

#24 PostAuthor: chrisw1 » Sat Dec 08, 2018 4:00 pm

great thread ........following with interest

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Re: Time to rebuild my old GPz

#25 PostAuthor: GPZ592 » Fri Dec 14, 2018 8:17 pm

As I've said earlier in this thread, this is not going to be a rebuild to standard spec and one of the upgrades I'm doing is increasing the capacity of the engine to 615cc. This means a 3mm O/S piston, but I'm not using Wiseco pistons, but Cruzin Image. Some may question that decision, but at 1/3 of the cost of the equivalent Wiseco kit, I thought I'd take the chance :D The CI pistons are cast not forged, but as this is a road bike and not a race engine, I do not believe this will matter.

I've already had the barrels bored by the guy that has done my engines for the last 30 years. He was quietly impressed with the CI pistons, declaring they "looked OE" spec and he's seen a few pistons in his time !

The crown height is slightly lower than the standard piston, but that doesn't bother me as the head has been skimmed in the past. In fact, the increase in bore means the CR turns out to be just about the same as the standard set up :D

CI Piston Kit

IMAG3790.jpg


IMAG3792.jpg


CI Piston against Standard

IMAG0131.jpg


IMAG0132.jpg
Last edited by GPZ592 on Mon Jun 01, 2020 11:46 am, edited 1 time in total.
"Racing is life. Anything before or after is just waiting" - Steve McQueen

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Re: Time to rebuild my old GPz

#26 PostAuthor: GPZ592 » Tue Jan 15, 2019 9:37 am

Not a huge amount of progress in the past few weeks, just a lot of cleaning/ inspection/measuring & listing of parts required :)

The engine cases were sent away before Xmas for blasting & painting, plus removal of a couple of sheared bolts. Similarly, the original Harris exhaust has been sent for blasting/painting, plus some remedial work. The header flanges that seal to the head were just turned up at the end of the header and were only the thickness of the header pipe itself, so have cracked over time. Later pipes I have seen had a collar welded on - a much better solution and one I'm looking to get done to my pipes. Also, the exhaust can has a couple of dents that need knocking out and the baffle needs to be removed to see is it's intact or rotted away !

Hopefully, the engine cases should be ready in a couple of weeks and then the fun will begin :D
"Racing is life. Anything before or after is just waiting" - Steve McQueen

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Re: Time to rebuild my old GPz

#27 PostAuthor: gpjes » Tue Jan 15, 2019 10:48 am

chrisw1 wrote:Brilliant bikes .....here is mine for some some inspiration
Is this Andy Whitley & his kwack 1100R in this pic? :D
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Re: Time to rebuild my old GPz

#28 PostAuthor: Pigford » Tue Jan 15, 2019 1:53 pm

gpjes wrote:
chrisw1 wrote:Brilliant bikes .....here is mine for some some inspiration
Is this Andy Whitley & his kwack 1100R in this pic? :D


Don't look like Andy - He's got a Z1R he sprints, but haven't heard from him in a while?
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Re: Time to rebuild my old GPz

#29 PostAuthor: gpjes » Tue Jan 15, 2019 4:27 pm

Pigford wrote:
gpjes wrote:
chrisw1 wrote:Brilliant bikes .....here is mine for some some inspiration
Is this Andy Whitley & his kwack 1100R in this pic? :D


Don't look like Andy - He's got a Z1R he sprints, but haven't heard from him in a while?
Must be two then, my mate Andy Whitley has an A4, he used his money from his 350lc and powervalve to buy Bill P's A4, never had a Z1R, but I have, hoho :D
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Re: Time to rebuild my old GPz

#30 PostAuthor: chrisNI » Tue Jan 15, 2019 5:47 pm

Pigford wrote:
gpjes wrote:
chrisw1 wrote:Brilliant bikes .....here is mine for some some inspiration
Is this Andy Whitley & his kwack 1100R in this pic? :D


Don't look like Andy - He's got a Z1R he sprints, but haven't heard from him in a while?



Andy WHITTLE Z1-R... :shock:


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