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View Full Version : Honda GB500 Thumper Performance Upgrades?



sammcj
23rd January 2009, 16:01
Project almost complete now.
Go to page 3 for details!




Hi All,

1987 Honda GB500 in overall good nick.

I know the first thing you're going to say... 'Get another bike...'
BUT
I really like this bike and... (I don't have the money for a sports bike! - Unless someone wants to trade heh)

I'm looking at spending upto $1000 on this bike to make it a little more unique / peppy, Is there anyone on here with ideas on what I could do / Where I could get it from (I'm in Christchurch) within my budget? (Cams, Electrical, whatever).

Or am I really, really wasting my time?

http://i66.photobucket.com/albums/h255/sammcj2000/P1010774.jpg

riffer
23rd January 2009, 20:58
$1000?

I seem to recall our illustrious site owner spent over $5000 on motor work (http://www.kiwibiker.co.nz/forums/showpost.php?p=315278&postcount=136) alone on one of these? He did end up with a pretty damn nice GB600 though.

Here's where you can get some performance parts for a GB500 (http://www.thumperstuff.com/GB500.html).

xwhatsit
23rd January 2009, 21:36
You could flog a Dominator motor from somewhere, that's a common mod -- cheaper than upgrading the original 500 motor to 600. The Dominator motor has a bit more poke, but is still a `thumper', it's relaxed and isn't very high compression. Met a guy who had a GB400 just randomly in Parnell who stopped to talk to me about my bike, he'd put a stock Dommie lump in it and was a happy chap.

I reckon the ideal would be getting a Dominator motor that's burning oil for cheap, then whack a high-compression Wiseco piston kit into it for a few hundred. You could do that under a grand?

pritch
23rd January 2009, 21:45
I wouldn't mind a stock GB500, I'd use it for a communter and for cruisy rides.

One of the mechanics at the local Honda shop has a GB 400 that he uses for a round trip of some 80 Ks each day.

piston broke
23rd January 2009, 21:54
overhaul the suspension and brakes

sammcj
31st January 2009, 11:52
I've decided to over-bore the engine to 600, changing piston to a 100x75 I think it was, should be done in two weeks time, I'll post photos etc... Can't wait!

sammcj
28th February 2009, 17:32
Just got the bike back.

Shes done 230km on the new engine so far!
Going for a ride to clockup 500-600 km if the weather is good tomorrow, then back to the shop on monday to do the tappets / carb and oil.

Bonez
28th February 2009, 17:43
Good one. I've got 84,000kms up on my 400. Once the motor packs up (at over 100,000kms I hope) I'm going the NX650 engine route.

sammcj
28th February 2009, 18:30
Good one. I've got 84,000kms up on my 400. Once the motor packs up (at over 100,000kms I hope) I'm going the NX650 engine route.

Oh sweet, that'll be a nice machine!
I'm quite impressed with the power gain from the 603cc bore, a lot better at 100k (@ about 4300rpm)

piston broke
28th February 2009, 18:58
hey so what is the suspension like?
the reason i ask is,i rode the old mans 500 and the rear let go.
swingarm bushes e,t,c are farked

Bonez
28th February 2009, 19:16
hey so what is the suspension like?
the reason i ask is,i rode the old mans 500 and the rear let go.
swingarm bushes e,t,c are farkedSwing arms probably never been greased in its life. Mine just flew though a WOF on Wednesday, inspector was a qualified m/c mechanic. Pack Gerbles on a regular basis and no problems at all. There's a grease nipple on the underside of the swingarm.

piston broke
28th February 2009, 19:26
Swing arms probably never been greased in its life. Mine just flew though a WOF on Wednesday, inspector was a qualified m/c mechanic. Pack Gerbles on a regular basis and no problems at all. There's a grease nipple on the underside of the swingarm.

it would'nt suprise me if it has never been touched.
the movement in the swingarm is very noticable:eek5:
it got me a beauty

Bonez
28th February 2009, 20:06
it would'nt suprise me if it has never been touched.
the movement in the swingarm is very noticable:eek5:
it got me a beautyYou should be able to get sintered bronze replacement bushes for them.

sammcj
28th February 2009, 22:19
hey so what is the suspension like?
the reason i ask is,i rode the old mans 500 and the rear let go.
swingarm bushes e,t,c are farked

Well mine is pretty mint, I rip it up round the port hills quite a bit and it's all good!

Paulo
28th February 2009, 23:23
Yes why would you want another bike? , these are sweet little machines, I 'm onto my second, sold the first and regretted it straight away so tracked down another 500. I ride it every day rain or shine, it just goes and goes and goes, Like bones said the warrants always been a breeze. Perhaps good advice about the dominator motor if you feel you need more oomph.
I just enjoy the fact that its fun to throw around the twisties and looks and sounds nice, I did put some sticky Metz tyres on and some Tomaselli clipons with a more extreme look then the stock ones. Thinking of putting them under the triple tree further down the forks if it not too much for my back.
They are getting really collectible in the states where they are considered a cult bike and they seem to hold there value. You probably know all this already. Nice to hear from another GB owner, good luck whatever you do. Yours looks great btw , I like the knee insert grips and the paint job, hang onto it i think it will only gain in value and rarity.

oops just saw your post saying you've done the motor already, Nice one! That will be one sweet bike.

sammcj
2nd March 2009, 22:51
I swear, I was on the damn thing all weekend (except when I got off at the sound of thunder!) It's going back in tomorrow to open up the jets a bit, off to the vinyl shop on monday for a new seat!

121216
121221
121222

Bonez
3rd March 2009, 04:26
I swear, I was on the damn thing all weekend (except when I got off at the sound of thunder!) It's going back in tomorrow to open up the jets a bit, off to the vinyl shop on monday for a new seat!
Welcome to the GB appreciation society ;).

sammcj
3rd April 2009, 17:22
Alrighty, Shes pretty much done.
New Clutch went in today.

One thing that is limiting it really badly (wont pull over 5k) is the muffler.

I'm now looking for one as cheap as possible!

droopydawg
4th April 2009, 00:40
Another good place to ask your question is on this U.S. site, especially for thumpers.

http://www.thumperpage.com/

sammcj
10th April 2009, 11:50
Next question: Spark Plugs.

Should she still be running the factory spec plug?

sammcj
10th April 2009, 11:50
Another good place to ask your question is on this U.S. site, especially for thumpers.

http://www.thumperpage.com/

Thanks, yeah I've seen that page, I don't think its updated anymore, there are lots of 404's on images etc...

Ojai
12th April 2009, 11:20
I swear, I was on the damn thing all weekend (except when I got off at the sound of thunder!) It's going back in tomorrow to open up the jets a bit, off to the vinyl shop on monday for a new seat!



I hear you. I picked up my GB400 on Friday, and I have been looking for every excuse in the world to go out on it ("No dear, I'll be glad to pick up some milk, I'll just dart off to Featherston for some...")! Even the ride back from Palmy at 10 degrees didn't put me off. What fun!

Paulo
14th April 2009, 09:58
I never get tired of riding The GB Just this morning I tagged a trip around the Miramar peninsula onto my commute, I've had this one for 4 years and it's still fun to ride.

sammcj
14th April 2009, 10:08
I never get tired of riding The GB Just this morning I tagged a trip around the Miramar peninsula onto my commute, I've had this one for 4 years and it's still fun to ride.

No wonder people are still hunting for these old bikes!

sammcj
17th April 2009, 15:34
New Dunstall Replica unboxing.

Paulo
17th April 2009, 16:06
ohhhh that's shiny , How much and where did you get it ?, My bike cover melted on my exhaust leaving a bloody mess (my fault really). looking good!

sammcj
17th April 2009, 16:07
ohhhh that's shiny , How much and where did you get it ?, My bike cover melted on my exhaust leaving a bloody mess (my fault really). looking good!

http://www.trademe.co.nz/Browse/Listing.aspx?id=212134063

The trader was excellent.




Congratulations on your Buy Now purchase!

Price:
$119.00
Shipping:
$15.00 South Island Courier
Total to pay:
$134.00

Ojai
17th April 2009, 16:10
New Dunstall Replica unboxing.

That is some hotness right there.

sammcj
17th April 2009, 16:12
That is some hotness right there.

Careful what you say about my cat ;)

SPman
17th April 2009, 17:23
They're like hen's teeth over here.......

sammcj
20th April 2009, 18:12
So that pipe wasn't free flowing enough aparently...

Ojai
20th April 2009, 20:51
You guys see this? http://www.trademe.co.nz/Browse/Listing.aspx?id=213897853

Any good?

Pinstripe
21st April 2009, 10:48
This thread is giving me ideas :yes:

Forgive my ignorance here, but is upping to a 600 simply a matter of fitting a rebored or XR600 cylinder and a wiseco XR piston, or is there a bit more to it?

sammcj
21st April 2009, 10:53
This thread is giving me ideas :yes:

Forgive my ignorance here, but is upping to a 600 simply a matter of fitting a rebored or XR600 cylinder and a wiseco XR piston, or is there a bit more to it?

You have to sleave the engine too.
Also, you have to rejet the carb and bore out or replace the exhaust.
It's also better go for the slightly older XR600 piston which results in something like 603 or 607cc rather than 575 or whatever it would be.

Pinstripe
21st April 2009, 11:49
You have to sleave the engine too.
Also, you have to rejet the carb and bore out or replace the exhaust.
It's also better go for the slightly older XR600 piston which results in something like 603 or 607cc rather than 575 or whatever it would be.

Cheers, looks like i have me a winter project :2thumbsup

sammcj
21st April 2009, 12:17
Cheers, looks like i have me a winter project :2thumbsup

Do it mate!
Need to see some more hotted-up GB's around!

sammcj
22nd April 2009, 20:05
Great News!

KG made up a new 100% free flowing muffler today, sprayed it matt black and OH MY GOD does it sound good and whats more I feel like I'm being thrown off my seat when I open her up!

Movies and Pictures to come soon!

Ojai
22nd April 2009, 20:47
great news!

Kg made up a new 100% free flowing muffler today, sprayed it matt black and oh my god does it sound good and whats more i feel like i'm being thrown off my seat when i open her up!

Movies and pictures to come soon!

Need! Need! Need!

sammcj
24th April 2009, 15:40
Very cool GB / XBR Project (http://66.102.7.132/translate_c?hl=en&sl=de&u=http://www.honda-xbr.de/pics/pics2.html&prev=/search%3Fq%3Dhonda%2Bxbr600%26hl%3Den%26sa%3DG&usg=ALkJrhh7mgEpmZ4Yfb9T81yltjiDxspIqA) -

sammcj
24th April 2009, 16:00
So... to sum things up since I got the bike a year ago:

-New Seat
-Hand Made Free-Flowing Exhaust
-Replaced Altinator
-Replaced CDI
-Replaced Voltage Regulator
-Replaced Coil
-Replaced Clutch and Break Cables
-Replaced and Reconditioned Carb
-Larger Main and Jet in Carb
-New Plug (still factory, anyone go any idea what I should change this to?)
-New Piston
-New Battery
-New Dunlop Tires
-New Leavers
-New Mirrors
-Valve Grind
-Block Bored and Sleaved
-Ignition Wiring Fixed
-Resprayed Headers
-Replaced Break Pads


Comming up...

-Koni Shocks
-Chrome Bar-End Mirrors
-Tank / Covers Resprayed (Might Go Matt black)
-Xeon Front Headlight
-New Stainless 2-1 Headers

sammcj
25th April 2009, 13:16
Two Quick Videos (sorry about youtube's quality)

http://www.youtube.com/watch?v=w6m7kdbr-xA

http://www.youtube.com/watch?v=Fa5oSTM03Ts

sammcj
26th April 2009, 12:37
Better photos & video

http://www.youtube.com/watch?v=qPEiJ1Lnv1M

sammcj
26th April 2009, 16:27
Need some clip-on mirrors...

Pinstripe
27th April 2009, 09:28
Lookin' good man :Punk:

maybe you should add a Davida lid and Halcyon mk.8/9s to your list too :yes:

warp
24th May 2009, 20:27
Just thought I would add my bit as Ive picked up another GB after .....how long ago was 1987?.
should be back on the road in a month. think Ive gone a bit loopy with the engine . spent so much on the suspension thought it needed a bit extra. XL Hot Rod and 11:1 piston . XL 600 Barrell
Most money has gone to CSL for the sprint grind , porting , big valves and light springs. and "choke" titanium collets.
Havnt had a smal bike in years , I had forgotten how much fun they are .

sammcj
28th May 2009, 11:30
Just thought I would add my bit as Ive picked up another GB after .....how long ago was 1987?.
should be back on the road in a month. think Ive gone a bit loopy with the engine . spent so much on the suspension thought it needed a bit extra. XL Hot Rod and 11:1 piston . XL 600 Barrell
Most money has gone to CSL for the sprint grind , porting , big valves and light springs. and "choke" titanium collets.
Havnt had a smal bike in years , I had forgotten how much fun they are .

Sounds like a beauty!
If it's in CHCH I'll have to see it!

sammcj
28th May 2009, 11:39
New mirror on...

drmikenz
21st June 2009, 12:11
New mirror on...

mint :yes:
just got myself a GB400 the other day and was wondering where you got the mirrors and the knee grips from ?

M

sammcj
21st June 2009, 12:12
mint :yes:
just got myself a GB400 the other day and was wondering where you got the mirrors and the knee grips from ?

M

Good on ya!
Mirrors were from Trademe, but I'm sure you could get them in a bike shop locally.

The grips were on ther tank when I bought it so can't help you there sorry!

drmikenz
21st June 2009, 17:08
no worries, i think motomail has bar end mirrors.. will keep searching for those knee grips!

off to have some konis put on in the next few weeks too once i've scraped together some cash :lol:

what did you end up doing with that dunstall replica ? is it the same loudness as the standard pipes or significantly louder ? my exhaust is pretty dinged up so will replace it some stage soon but don't really want to go much louder than standard..

sammcj
21st June 2009, 17:12
no worries, i think motomail has bar end mirrors.. will keep searching for those knee grips!

off to have some konis put on in the next few weeks too once i've scraped together some cash :lol:

what did you end up doing with that dunstall replica ? is it the same loudness as the standard pipes or significantly louder ? my exhaust is pretty dinged up so will replace it some stage soon but don't really want to go much louder than standard..

I had to re-sell it, it was far, far too restrictive, got a custom made straight through pipe made up :D

drmikenz
22nd June 2009, 08:26
I had to re-sell it, it was far, far too restrictive, got a custom made straight through pipe made up :D
bugger, i would have bought it off you. what was the sound like compared to the stock ? i've heard the sound of your straight through on youtube, very nice but a bit loud for me ;)

sammcj
22nd June 2009, 08:30
I didn't even put the pipe on in the end, you can pick them up on trademe for about $80+shipping.

I wouldn't recomend it, they're really designed for at least a 2 cyl bike.
Mine is a 200cc bigger than the GB400 of course mind you.

vinducati
22nd June 2009, 11:08
Deus ex machina have opened a shop in Auckland near Victoria Park Market , on Wellesly Street.
Check it out, very nice custom SR400, WS650, Bonnies,
also good Cafe and Clothes.
It's in the old Powerboard warehouse which is mainly a carpark area.
They also have a website based in Australia.
They have just opened and makes other bike shops look a bit sloppy.

Gerard
18th July 2009, 03:29
Hello.
Please, what brand and model piston is ?
And sleeve ?
Stock sleeve re-boring?
XL or XLR 600 sleeve?
If XL or XLR sleeve, motor cases hole re-boring?
And what is your cylinder head gasket now?
Thank's for infos.
Bye,
Gerard.
France.



I've decided to over-bore the engine to 600, changing piston to a 100x75 I think it was, should be done in two weeks time, I'll post photos etc... Can't wait!

The Pastor
31st July 2009, 09:14
Hello.
Please, what brand and model piston is ?
And sleeve ?
Stock sleeve re-boring?
XL or XLR 600 sleeve?
If XL or XLR sleeve, motor cases hole re-boring?
And what is your cylinder head gasket now?
Thank's for infos.
Bye,
Gerard.
France.
I'd talk to your local motorbike mechanic mate.

sammcj
31st July 2009, 09:17
Hello.
Please, what brand and model piston is ?
And sleeve ?
Stock sleeve re-boring?
XL or XLR 600 sleeve?
If XL or XLR sleeve, motor cases hole re-boring?
And what is your cylinder head gasket now?
Thank's for infos.
Bye,
Gerard.
France.

Hey,

Can't really remember sorry.
It wasn't a stock sleeve thats for sure.