T500 - Max Power Reliably?

Frank · Post by **Frank** » Wed Oct 28, 2009 6:35 am

I'm kicking around the idea of converting my '73 T500 into a land speed racer which involves full-throttle acceleration for up to 1.5 miles. What kind of power have people seen from these old sleds? Is 100 hp possible normally aspirated? Has anyone ever run nitrous? I have a '71 parts bike also.

Thanks,
Frank

gyrocfi · Post by **gyrocfi** » Mon Nov 23, 2009 4:08 pm

Well, I guess I can chime in. The post looks pretty sad with no responces.

I didnt ride the T500's but put LOTs of miles on the GT500s. Just a few intake changes by suzuki and CDI ignition. I rode the crap outa mine in the mid70s, full vetters fairing, saddle bags, luggage rack. Most of the time on the interstate I did 75-85 indicated (most likely with speedo error 70-80). Before I put the fairing and bags and after 2K breakin I pulled a full power run to see how fast it would go, laying on the tank feet on the tail lite I got indicated 120, most likely really 110-115?? couldnt get it to red line in 5th but I wasnt really trying. 120 was PLENTY fast enough in those days on that bike!!!!

On my GT500s now I push em less but have run an indicated 95 for a few miles when I get a wild hair. but I want mine to last till the Feds band 2strokes from the road or I die so I take it way easier than I did 30 years ago.

So, I think you can infer from what I wrote most likely a 100mph wouldnt be all that hard on the old T500 if properly prepared. The guys doing vintage road raceing are doin that plus routinely, highly modified for sure.

rngdng · Post by **rngdng** » Mon Nov 23, 2009 7:33 pm

100 mph, not a problem, but 100 HP??? That might be unrealistic. The TR 750s barely made more power than that. 75 HP might be done, but even that isn't easy or cheap.

Eric, what's the most you got out of a T500?

Lane

water cooled · Post by **water cooled** » Mon Nov 23, 2009 8:26 pm

Frank, I agree with Lane. 100 BHP would be a very tall order. If your interested in land speed, start looking more at snowmobile technology instead of what T500 road racers have done. I'm in a similar boat trying to get 114 RWHP from a GT750 and that's a very tall order.

I think you should pursue your idea of racing on dry lakes...I would love to follow your progress over time.

Frank · Post by **Frank** » Mon Nov 23, 2009 8:38 pm

Thanks for the replies guys. I expect 100 hp isn't going to happen but was trying to get discussion going. The class I'm thinking about is production (internal mods are allowed but external appearance has to be maintained.) Speeds jump quickly when you start looking at special mods allowed classes. If I wanted to go really fast I would just run my stock Hayabusa but I'm looking for a way to use the T500. I've heard of people cutting open stock exhausts, modifying in various ways then welding shut, grinding, rechroming, etc. All legal as long as it looks stock!

Zook-e · Post by **Zook-e** » Mon Nov 23, 2009 8:41 pm

rngdng wrote:100 mph, not a problem, but 100 HP??? That might be unrealistic. The TR 750s barely made more power than that. 75 HP might be done, but even that isn't easy or cheap.

Eric, what's the most you got out of a T500?

Lane

I've gotten close to 80HP but it becomes real peaky with maybe about a 1,200 rpm power band. The stock trans is crap for this HP. A six speed would be good and a set of reeds.

Craig380 · Post by **Craig380** » Tue Nov 24, 2009 2:58 am

Can you use fairings on a land speed racer? At 3-figure speeds, anything that cuts aero drag will make a big difference.

Back in 1963 when Yamaha first took their RD56 250s to the IoM TT, they caused a sensation when Tony Godfrey went through the speed trap at 139mph ... that was just 2mph down on the MV350-4, and Yam claimed about 45bhp ...

Frank · Post by **Frank** » Tue Nov 24, 2009 9:01 pm

I'm looking at ECTA rules; "production class" means stock looking, as it came from the factory. There's a bunch of other classes but as soon as you add a fairing you're no longer in the same class (unless it came from the factory with one.) There's some safety mods required (ex. you need a handlebar kill switch and lanyard activated kill switch), you're also allowed somewhat lower bars.

Actually what I'm planning to talk to Eric about is porting for stock-exhaust bikes and head work. I'll split the cases and probably send the tranny to R&D to backcut, magnaflux and do their usual stuff. That would hopefully give me a sweeter running street bike and something I can play boy-racer with.

I now have '71 and '73 parts bikes but the '73 is a little stuck.

Eric, do you think a massaged stock tranny could handle 60 hp? (I'm guessing that's what I might get.) Other questions are: is it worthwhile to think about boring stock carbs? Is electronic ignition worth it?

thanks,
Frank

johnakay · Post by **johnakay** » Thu Dec 03, 2009 12:06 pm

I don't know about HP'S but I used to know a lorry driver who use race them in the early 70's and he claim he used to get 146mph out of his T500.
what state of tune I don't know.
when I had my T500J in the 70's.
I had the barrels and head tune by Eddie Crooks(crooks suzuki) I could get indicated on my clocks just under 135mph so that would probably do about 120/125mph. anyway I had the fastest bike in our group

in standard trim it used to indicate 115mph.
anyway when it came to the twisties my mate won hands over.
he should've been a racer.
how he handled them bikes I just don't know but he was bloody good.
met him a few years ago and he said that I was a good rider here's me thinking otherwise.
I suppose its just how other folks see you!
I don't think I was bad but certainly not good.
in all the years of riding bikes I only came off 3 times but scooters(Lambretta's)from 68 to 70 god knows.
I was always coming off every other week. could never get around them corners and ending up in a farmers field.

once I tried to overtake a double decker bus on a lammy 150cc and ended up in a middle of a round a bout.shoulda seen them faces on the bus me my face was like a beetroot

ja-moo · Post by **ja-moo** » Thu Dec 03, 2009 6:39 pm

Jughead was on the fast track to see how my reedvalve conversion would work on the Suzi 500's but now he had a dame, so who knows when........

evol02 · Post by **evol02** » Thu Dec 03, 2009 10:24 pm

hmmm, one of my old lammys had a 225 kit, stage 6 tune and a 32 or 34mm carb on it, that thing could get up close to 100 mph on those little 10" wheels. sort of glad i got rid of that beast.

I'd be very curious to see what you manage to squeeze out of that Titan!

tz375 · Post by **tz375** » Fri Dec 04, 2009 10:21 am

What is the world coming to. Lambrettas.

One question that Frank raised was his pipes. The simple answer is yes the pipes can be opened up and a reverse cone and stinger added. The RD boys used to do that all the time in their "production" class. Most kawasaki triples have a simple expansion chamber design inside, but Suzuki and Yamaha are quite different.

I'm sure we can modify those pipes and if anyone has the stock pipe dimensions, I'll work out what we should do to them.

That raises the obvious of how close to stock does it have to be and how far can the truth be stretched? Exactly right - almost right - kinda sorta resembling it - not even close. How far along that spectrum can we push it?

34mm carbs bored to 35.5 will slot straight on I think and no one would be any the wiser but going to 38's might be a stretch. Maybe not.

Flatslides would be nice but noticeable. Can you cut down the seat foam like an early superbike or is that verboten? If not, trim an inch or two out of the whole seat and recover it and no one will notice.

Get it ported and squish heads ( get some spare stockers for the street) and you should be looking at 125 plus. Above that it takes huge HP rises to get the extra speed.

tz375 · Post by **tz375** » Fri Dec 04, 2009 10:45 am

I read the ECTA rules and they are quite clear - it must look stock and the rider has to provide the documentation. Photoshop anyone?

The exhaust and intake rules are clear 00 it must look stock and no big bore exhaust. That shouldn't be a problem but the exhaust noise might be a giveaway.

There's lots of empty P/PV record slots to fill and I don't see you having too much trouble nagging a couple of spots.

An almost stock GT750 with porting and modified pipes could make its matk too.

Frank · Post by **Frank** » Fri Dec 04, 2009 9:30 pm

You're exactly right: it has to look stock. That says to me that porting and head work is okay, stock carbs could be bored (I don't know what the practical limit is: is it 35.5mm?), electronic ignition, exhaust pipes could be cut apart, modified and welded up again. I'd prefer to start w/o modifying exhaust pipes as that's a lot of work.

Lower bars can be fitted (there's a limit and I can't remember what it is) but rear pegs have to be removed, side/center stands can be removed.

I have both '71 and '73 engines available: any thoughts as to which one would be best to start with?

Jughead · Post by **Jughead** » Mon Dec 07, 2009 10:49 pm

ja-moo wrote:Jughead was on the fast track to see how my reedvalve conversion would work on the Suzi 500's but now he had a dame, so who knows when........

An Ol' Lady and Starting another business.

You never know may be sooner than you think.

T500 - Max Power Reliably?

T500 - Max Power Reliably?

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