Honda GB500 tt

[Kwaka-Kid]

Spankme mate! Stuff lightening the flywheel i have about 5x XR/L500 flywheels here on stock, your better off bolting on one of them dude.

As for Alex Gee? hahahaha, yeah ummm, go with colemans! -do you know him personally Frosty?

Better yet ill find out for you today spankme from only the best in the trade.

[gav]

SpankMe, this could be useful for you?
XR600 barrell & piston
Of course you could end up with something like this

http://www.moonpie.co.uk/ikuzaw_1.htm

[gav]

Some more useful sites, but I guess you may have already found them?
GB400TT Tune improvements
its been translated from Japanese so a little hard to follow!
Shame Honda never released this!

[Kwaka-Kid]

Spankme: The GB500 is alike the XR600 and odd bits and pieces will swap but pistons etc do differ somewhat. thats what i was told today man and it sounds like you just have to go off what people tell you from experience. Things like XR600 cranks etc can go in with some filing of engine casings etc and other bits and pieces.

[SpankMe]

I'm getting a big bore kit made for the GB500 by White Brothers so should be no problem there. Wasn't looking at doing the crank shaft, but will replace the cam shaft with the one used by Cycle World. As for the carb, I will get the Mikuni one as the carb kit is probably setup for dirt bike engine, not road bike.

I would also prefer replacing old parts with new ones than replace the engine with a second hand one.

Will have to look further into this flywheel thing.

[Bonez]

Some more useful sites, but I guess you may have already found them?
GB400TT Tune improvements
its been translated from Japanese so a little hard to follow!
Shame Honda never released this!

I'm not a "race bike" fan but I certainly do like the look ofthat.Can't wait for the mid-life crises to kick in

[SpankMe]

Has anyone had their engine ported and polished? Thinking about having this done as part of the engine rebuild.

Any idea of cost and level of technical skill required to do it. And is there any shop in Auckland that can dot it?

I want to get the engine in as good a condition as I can after the rebuild. This bike is gonna get a lot of use.

[Blakamin]

Porting isn't a bad idea.... but there's a few different views on polishing.... sometimes a polished head will not create any turbulence, therefore, not having an efficient burn pattern....
some say it doesn't matter....
just a few debates that have gone back and forth in the drag-racing world for the last 15 years (that I was into it)

:spudwhat:
as your link says, porting is just cleaning the castings and trying to "straighten" the mixture run to the chamber.... not hard with a dremel if you have no water jackets to grind thru too... at least you dont have 8 cylinders!!! thats where the pros are handy coz they'll gas-flow the head to get them equal
polishing is a pretty DIY type job too..

[edit] port matching is a piece of piss too... just put a bit of bearing grease around your intake and sit in in position.... take off and look at the head.... scribe inside grease and dremel away....

[Kwaka-Kid]

If you thinks its beyond you Spankme i can recommend HPE Engineering down in the south island, not from personal experience unfortunatly but they have been recommended (Actually for Sleeving etc but im sure they will port/polish for you) And Blakamins onto it, if you ask my old man if you should port/polish he will say hell yes and rave on about it, go ask the next old guy beside him and hed say dont bother with the polish, who knows, im sure there have been studies that support both ideas :S... BTW Spankme does that beast have a single carb yeah? if so have you slapped at LEAST a 40mm on there yet? Im using a 40mm with a 147 main jet atm on XR500 will get its first proper run with sealed exhaust next weekend... will let you know how she runs, then i might even move up to the 41mm carb - but hell it was a massive effort hammering the 40mm into the std XR500 rubber designed to take a 36.

[SpankMe]

These guys used a 41mm Mikuni carb, so I will do the same. Well the Colemans mechanics will be doing the same.

Will have to contact HPE Engineering to see what they charge for a port and polish.

[Kwaka-Kid]

Yeah spank. and yep on the 41mm carb i have a Mikuni Pro series flat slide mechanical carb, and my 40mm is the same only its a pumper carb aswell (Though im missing hte pumper rod so not acting as pumer atm)

Please do let us know what size main jet colemans end up with in your bike. Also you do realise once you go to the massive 41mm carb you completely loose the airbox and go to Sportspro or the likes and buya Uniflow big air filter just to bolt straight on the back of the carb... otherwise the airbox and std filter even with replacement twin air filiment is not enough. Also those big mikuni pro series carbs are shorter then std and it wont reach the rubber that comes from airbox-to-back of carb... there is a 1mm gap so no overlap, i have had to duct tape mine to seal just untill i get around to going to sportspro.

[What?]

Don't polish the inlet port - the fuel mix is likely to condense on the smooth wall, thence it won't burn properly.

If you want to hot-rod the engine, I strongly suggest you talk to Rex Danby in Thames. The man knows his stuff.

Danby Machine & Development Ltd

Cochrane St Thames
0-7-868 8284

[SpankMe]

I was at Cyclespot Honda today asking about recommendations for a shop to do the engine work and the guys in the parts department suggested a guy at performance engineering across the road. He said the guy has a lot of experience with XR engines which is just what I need from a mechanic if he’s going to work on a GB500 engine.

[F5 Dave]

For a few hours reading (entertaining)

http://mototuneusa.com/

You have to subscribe, but haven’t had any drama from them. Basically there are several articles on porting which rubbish the bigger is better philosophy many adhere to (skip through to the porting articles).

If you go for max flow you will get an engine that is a bit unpleasant in the lower rev range. The problem with looking at a port esp with a flow bench is that you assume the valve is always open & the flow is one direction. This is an assumption & not a very good one.

PS did you ever get hold of Si or did he jerk around?

[Sensei]

Hey SpankMe Freind down here just put a XR650 into his GB500 frame with a heavy Fly wheel on it . This bike was seriously quick . Another guy I know race's a GB500 only has carb & pipe he has made himself , as he make's them for a living . If you need to talk to him can give you his number .
SENSEI