Still not running right ..

[matthias]

My bike is still running horribly after a 50,000 mile rebuild. So here’s the story so far… I originally bought this bike ‘accident damaged’ in about 1999, got it going and sold it to a friend. It turned up in the back of another friend’s shed about five ago, where it had apparently languished for about twelve years. I bought it back out of sympathy and for something to do during ‘lockdown’ and I’ve been fiddling with it since. It runs but it won’t start easily or respond well to throttle. This is what I’ve done so far:- Top end stripped, cleaned and rebuilt with new gaskets, o-rings and small end clips. Valve clearance/shims done. Clutch rebuilt with Viton dampers. Cylinder compression is at the bottom end of the acceptable range but consistent across all four cylinders. New BR8ES plugs, NGK caps and leads. Evergreen have completely rebuilt the turbo with a billet wheel and also cleaned and calibrated the injectors. No apparent fuel or air leaks. Fuel pressure checked and set at 35-36psi. (Mike Chestnut adjustable FPV). Return valve on fuel tank cleaned and working. Fresh E5 fuel. Standard air filter, plenum box etc. Predator single pipe exhaust. Complete rewire (both looms) by Rupes Rewires. TPS replaced, tested and set. It's not in race mode and there's no warning lights on ECU. . . What to check/replace next?? Btw - Are there any motorcycle mechanics in Cornwall, UK that have decent knowledge of these bikes? Thanks

[Mrredt]

What colour are the plugs after a run
What injectors
What adjustments have u made
Drain tank down
Put a gallon of fresh fuel in
Change the fuel filter
Maybe check timing
Adjust tps

[Charlie @ Evergreen]

Usually run BR9ES plugs, with billet turbo you should be in race mode with the extra flow and the turbo is setup for higher boost level past the cutoff without race mode. Reset TPS properly there is a setup link on how to. Fuel pressure with this setup should be in the 40-41 lb range then setup TPS. Maybe its just not tuned right causing issues??

[JezZedexE1]

Predator single pipe exhaust.

Although it should not make any difference, if the Predator exhaust you have is similar to the Predator I had at one stage, it may be a good idea to measure the I/D & O/D of the pipe where it connects to the turbo unit. Mine was a smaller diameter, which I presume would have been a bottleneck for exhaust outlet flow.

[matthias]

Hi Charlie. Thanks for your reply. I'll get some BR9ES plugs and have another go at it later this week. I'll run it with a dummy tank to make sure the fuel is returning properly and also re-check the fuel pressure, fuel filter etc.. Excuse my ignorance but I didn't know that it needed to be in race mode with the billet turbo. I've been reluctant to cut the brown wire. Am I not right in thinking that some form of resistor then needs to incorporated?? I'd like to getting it running properly before I try making too many changes. It's currently standard apart form the billet turbo and Predator exhaust. My original TPS was showing 'jumpy' readings so I've managed to obtain a couple of decent ones from a member and done my best to set the TPS. They all give slightly different readings, with regard to resistance and signal voltage. The one I'm using has the blue/white wire showing 4.62v on tickover, dropping smoothly to 0.73v at WOT. Does that seem ok? I've tweaked it to get the best tickover and then backed off the idle screw. It's happier with the TPS turned slightly to the left (anticlockwise) but whatever I do, it seems to be running rich. The plugs are black and sooty. When I fire it up it kind of '8-strokes' with black smoke. When it clears, the tickover is erratic and sometimes the revs are slow to drop when I throttle off. If I try to ride it, it won't rev more than about 4-5000rpm.. I don't think there is anything fundamentally wrong with it and as you say, it probably just needs setting up properly. I'll have another look at the fuel pressure etc. Do you have a link for setting up the TPS properly plz? I haven't checked the boost sensor. Could that be having an effect? Cheers, Matt

[matthias]

Hi JezZedex1 - thanks for your suggestion. I don't think this could be causing the issues I'm having but I'll whip it off and have a look when I have another go at this bike later in the week. Cheers, Matt

[JezZedexE1]

Link to TPS setting:
viewtopic.php?t=18625

You do not need to cut the brown wire. As I understand it, it just needs to be removed from the connector block.
viewtopic.php?t=13395

[matthias]

Very useful and interesting! Thanks for the links. I will be studying all of this info before I pull it apart again later this week..

[matthias]

Ok - got the plugs,just need a variable resistor now. Is there a recommended one? Will this type (5 k Ohms version) do it?.. https://www.ebay.co.uk/itm/382850392801 Am I right in thinking that the variable resistor goes between the brown and red/blue wires, both of which are disconnected from the ECU box? To be continued... Cheers, Matt

[JezZedexE1]

I have done this.

Screenshot 2026-01-28 113938.jpg (69.74 KiB) Viewed 11202 times

Look about, there will be other places (like in the "HOW TO" section) which has some info.
viewtopic.php?p=192175&hilit=race+mode#p192175
viewtopic.php?p=192080&hilit=race+mode#p192080

[matthias]

Perfect - thank you Jez

[SilveradoKC]

For what it’s worth I’ve owned two of these - both in stock and modified forms - and never had a resistor and never had any problem running whatsoever

[matthias]

That’s good to hear. However, I think my old girl might require some electronic intervention before she’s happy

[JezZedexE1]

My guess it is a set-up issue or something like an air leak. The more you mod the electronics/electrics, the more difficult it will become to resolve the issue.

[matthias]

Hi Jez. I'm a bit confused now. According to Charlie Brown (see reply Jan 24) with the billet turbo fitted I now need to be in race mode with the variable resistor and increased fuel pressure, if it's to run right? - so that's the route I was taking. I've got BR9ES plugs for it, the variable resistor should be here tomorrow and I've now got a decent TPS to use. I'm going to have another go at it over the weekend. Are you saying that I should try and get it running ok before I wire in the resistor etc?