Power out of T500

[merckid]

Ive been thinking lately about making a race engine for my T500. What are some things that you guys have done to gain power from T500 motors?

[tz375]

At the risk of seeming to be glib, the answer is pipes ports and carbs plus heads.

If you are in the UK, PEDRO is your go to guy for racers. In the US, talk to Eric Zookie. He has prepared a few race bikes from mild to wild depending on the race organization rules and what class you plan on entering.

For example AHRMA's Historic production class limits modifications, but WERA's F500 is pretty open as is AHRMA's F500 class.

[Zunspec4]

Hiya kid (sorry couldn't resist that )

I can tell you what was done to my TR500 spec (ish) race motor which I believe made 70+ bhp.

Stock rods and big ends on a lightened crank + crankcase stuffers to maintain the primary C/R

Straight cut primary gears

Krober self generating ignition, which on my bike was set at 3.7mm BTDC

Barton Close ration 5-speed gear box

Modification to the clutch basket in that somehow there was an extra set of plates (Honda plates, I think)

Barrels ported by a guy called Mick Hatherill (RIP) and superbly matched to the crankcases.

Standard GT 750 pistons with 1mm machined off the skirt. Changed every 5-6 meetings, rings every 2-3 meetings.

38mm racing Mikuni carbs, not sure exactly what model they were

Works centre plug heads

Unknown pipes but the motor would come on really strong from just below 7000 rpm and sharply tapered off at around 10,000 rpm.

The motor used the standard oil pump but it was simply hooked up to full flow (using a bicycle spoke ) just before coming under racing orders. Castrol R30 was fed from a tank in the seat tail.

Basically a fair bit of work even when there were tuning parts available back in the day.

Cheers Zunspec

[tgrogan]

Do yourself a favor and go for the easy fundamental changes like TZ350 said. Grind some on the ports, get a set of appropriate pipes, and get some larger true VM carbs. You will quickley find out that you will be able to way outrun the chassis. Then spend some serious money getting the chassis to work. You will loose more track position with poor handling than you will gain with the difference between 60hp vs 80hp - and it's absolutely true unless you get a aftermarket transmission.

[tgrogan]

Pedro, please refer to me as Terry. I may be very old and did my racing back in the 70-80s, but I still don't need 'Mr'. :>)

I think you need to realize two things. First, there is a huge difference between GPB and $US - almost x2. Second, we don't have access to the type of modifications that you folk in the UK can relatively easily get done. That said I would like to restate some of what I said based on the above.

Doing porting, chambers, and carbs is relatively simple stuff that can be done by an individual maybe with some slight help by a semi-skilled mechanic. Hence, my saying that around 60 hp + would be a reasonable goal. At even this level the chassis is woefully inadequate. You must cross brace from the swing arm to the steering braces, replace swing arm and steering head bearings, and move rear shock mounts forward. With these things done, I believe that 80-90% of the potential of a T500 has been acheived - and this is my point!

Any more modification is moving away from being a T500 into being a Franken-T500. Sure you can pour thousands more and make up for all of the 'short comings' of the T500, but do you really have a T500 when you are done?

I'm not trying to condem what you do. All I'm saying is that there is potential for a whole lot of racing enjoyment long before the 'ultimate' T500 is built.

[tgrogan]

Why do you say you can't get stuff done as easily as we in the uk can? I realise the travel distance is far greater, but I would have thought you have far more divergence of facilitys than us in the UK.

Not actually for finding someone really interested in old 2-stroke racing. I believe that besides Eric Zookie there might be one or two more resources. Resources in this country tend to be quite focused on a narrower part of technology than I believe you experience in the UK.

As for "Doing porting, chambers, and carbs is relatively simple stuff that can be done by an individual maybe with some slight help by a semi-skilled mechanic." Relatively simple ...... relative to what??? I

The chambers and carbs are purchase items - no problem there. Porting diagrams are readily available for, and easy to grind, for the T500. I have the original spec sheet for making a T500 racer from Suzuki. The porting consists of just straight opening up the intake and exhaust ports by 5mm with nothing done to the transfers beyond a little cleanup. Not much beyond the slightly above average dirt bike mechanic. I did mine and I had never even held a air grinder before. Not saying you'll get a 10,000rpm screamer, but I won a ton of races with it back in the day. Could run with heavily modified 750s, and chase 1000s quite close.

, and your T500 will still look like a T500 nothing franken about it.

Maybe look like, but you just put 2000Gpb into a T500! Without working on the engine, if that's not 'franken' I don't know what is! I only listed the bare minimum to keep from killing ones self on the first corner, and maybe being able to fight you way around a few others. I think that you made my point about just getting started with 'some porting', carbs, and chambers is more than enough to totally outrun the chassis.

Congrats on keeping up with the racing. I've 'retired' to a Ural hack rig and am really enjoying it. It's just as easy to work on and modify as a T500, and my wife comes with me instead of bit&$ing about me riding. I still have my 68 racer together in the garage. Keep saying I'll get it running again.....

Regards,

Terry