TR500 won't rev over 6000rpm

[ben james]

Hi People,
I have a John Woodley TR500 that won't rev over 6000 rpm. It has TR barrels but just stock T500 heads with 34mm carbs. 3.1mm BTDC timing. I got the bike from a friend who also races these bikes and is quite knowledgeable about them but it has us stumped. I've tried jetting from 310,300,290,280,270 & 260 with no difference. The only difference from when he ran it is fuel. He ran it on Leaded Avgas which is no longer available in Australia. I'm using Power Plus 102 Unleaded race fuel. Any thoughts on this situation.

[ben james]

photo

[ben james]

sorry forgot PVL Ignition

[Zunspec4]

Hello Ben,

I assume that previously the bike would rev to something like 8 - 9000 rpm. I don't think the difference in fuels would cause any drop in performance to the extent of limiting the rpm to 6000. I would suspect there is something amiss on the ignition side. As a simple test fit a new set of plugs, I have had problems with plugs going "off" on my race engines. If that makes no difference you are looking at the PVL ignition components.

Cheers Geoff

[joolstacho]

Do the alternators on these have low-speed coils and high-speed coils?

[ben james]

It's a self generating unit with no battery

[tz375]

Nice looking bike.

Sounds like ignition. I'd start where geoff said with plugs and leads. If that won't fix it, take the ignition off and bench test it on a jig.

I use a router to drive mine.

Is that an HMRAV logo?

[Suspensionking]

hello Ben

That a very nice looking machine, I race one of those in the Spanish championship. I think Geoff is in the right direction with the Ignition. I had similar problem with the PVM on mine 3 years ago and we changed it to one that was n^made in Belgium. ( I can find out the make from the person who preps my engine) Mine revs to around 8750rpm. I run 36mm carbs and we have cylinder head two gauges and to balance the temperature on the 2 cylinders we have been running 230 & 240 mains or 240 & 250 depending on the day and the circuit. I believe we could go even lower. I also experimented with fuels. I tried Elf race fuel 105 octane AND EWS FROM FRANCE 110 octane. However we found that burned too slow and ended up going back to 98 octane unleaded pump fuel and it seems to run best on that. We found on the 105 & 110 octane fuel it would only rev to 8000rpm.
Now that could be unique to my engine. My cylinders are standard T500 but the heads apparently came from Eddie Cooks and were made fro the TT. to be honest I am not sure what the difference is. However the bike is competitive I have had a win and a 3rd this year with the bike.
Well I hope this helps.

cheers

Eamonn

[ben james]

that is a HMRAV logo, great club. Very interesting about the fuel as that is the only change since it apparently ran well on Leaded Avgas.

[ben james]

I assume that previously the bike would rev to something like 8 - 9000 rpm. I don't think the difference in fuels would cause any drop in performance to the extent of limiting the rpm to 6000. I would suspect there is something amiss on the ignition side. As a simple test fit a new set of plugs, I have had problems with plugs going "off" on my race engines. If that makes no difference you are looking at the PVL ignition components.

Cheers Geoff
Hi Geoff, What sort of plugs do you use, I'm using NGK B9HS, One thing I have just done is fit a 3/8 NPT Pingel dual outlet fuel tap. It had these 2 brass taps that had an internal diameter of 4.5mm that I was unhappy with, didn't like the flow rate. Am going to put bike on dyno & see if any difference.

[tz375]

that is a HMRAV logo, great club. Very interesting about the fuel as that is the only change since it apparently ran well on Leaded Avgas.

Avgas is not noted to be a fast burning fuel. But di you actually use Avgas or Shell 100? That's what my son ran our TZ350 on and that bike would rev just fine on the same ignition timing we use in the US.

Back in a prior life, I was a member of the HMRAV and before I moved to the US, I was the Prez back when I was racing a Cb77 on methanol. Small world.

Back to your bike again: You could see if it's possible to buy a couple of liters of avgas from someone just to eliminate that as a possibility. New plugs, leads and caps might change something, but it sounds like the ignition system. Is there any chance that the timing has slipped? If not, I'd run it up on a dyno with a timing light and see if it does anything strange. That way you can also see the Air:fuel mixture

Dynobike in Moorabbin could do that for a reasonable fee.

[Zunspec4]

Hi Geoff, What sort of plugs do you use, I'm using NGK B9HS, One thing I have just done is fit a 3/8 NPT Pingel dual outlet fuel tap. It had these 2 brass taps that had an internal diameter of 4.5mm that I was unhappy with, didn't like the flow rate. Am going to put bike on dyno & see if any difference.

Hi Ben,

I run NGK B10EGV plugs. These I think have been superseded so I get mine from eBay. Your "9" is only one grade hotter (or softer) than my 10's so if it is working OK in your set-up I would leave it. +1 on a hi-flow fuel tap, I have holed a piston due to inadequate flow to the carbs causing leanness. I now use a pair of fuel taps designed for methanol which flow much much faster.

Modern unleaded fuel burns faster than the old 5 star leaded or 100LL Avgas. If you do run neat premium unleaded I would advise not to advance the ignition more than 2.9mm BTDC. I run less advance than this with 50:50 unleaded/100LL Avgas.

You have really nice bike, here's photo of my T500 to gee you along



Cheers Geoff

[ben james]

nice Frame

[ben james]

Pingel fuel tap, see if this helps

[ben james]

better photo