So I've recently had my 'blade back on the road. Went for a drive last week, and seemed fine, but when I got to some decent roads and gunned it, it was stuttering and popping above about 8000rpm. Further, when hot and ticking over it seemed to miss a beat every now and then - kinda stutter but then carry on.

My initial assumption was that it was ignition - perhaps spark jumping from plug cap to block (one of the plug caps wasn't in the best of condition, and the HT leads have "seen the manifold" a time or two). So today I made up some new HT leads, using brand new NGK plug caps and new HT cable.

Went for a drive today when the rain finally bogged off, revved to the limit fine when I was warm, but as soon as it got "properly warm" it was exhibiting the same symptoms - can't rev past about 8500/9000, popping and banging.

Engine was out and apart over the winter, but only to replace the gearbox - top end wasn't touched. Fuelling should be fine - I had it setup on rolling road last year, and as I say the explody bit of the engine hasn't been touched. I've stripped and cleaned the carbs since they've been layed up a few months.

So, any ideas what would make it run badly when hot, but run better when just warm? I'm loath to take it to a rolling road again having done it so recently, so could do with some ideas of how I can diagnose for sure whether there's an ignition issue, a fuel issue, or something else that temperature could influence?

Sooo need to get this working - haven't done a track day since 2011 and itching to get back on it!

Thanks


Simon

Fuel pump?

Might be worth checking the coils, one could be breaking down when hot. you also don't mention the plugs, would stick a fresh set in to at least rule them out.

Also if its been stood a long time i would be looking at the carbs again, they can be a pig to clean out, sometimes one clean is not enough.

Al.

It's got to be fuel or spark.

Blades are extremely sensitive to poorly plugs, it would be worthwhile swapping out for new.

On mine even little changes to the air box or exhaust caused issues as you have described, leaving the filter off for instance would give flat spots and stop it revving cleanly.

Cheers.

Have ordered some new plugs. Will give the carbs a second going over whilst I wait for them to arrive.

Would be surprised if it's fuel pump, it's not really near engine so shouldn't be affected by heat? Similarly ruled out fuel filter for the same temperature-sensitive reason (though I may swap that anyway since it's cheap).

If it's coil packs breaking down when hot, I presume there's no easy way of knowing without buying and fitting replacements?

The car currently has my home-made airbox fitted. I had it rolling roaded with the box on last year, and then he re-ran it with the sausage filter on - fuelling was fine with either (in fact was slightly better without the box, the stage 1 dynojet couldn't get it 100%), so I guess another test would be to see if it behaves any differently without the box on, and give an indication as to whether it's a fuelling issue.

I had exactly the same behaviour a couple of months ago, after the winter.
Engine pushing as expected until it's hot, and then it runs poorly after 8000 t/min.
In fact I didn't purge the water circuit correctly, the water was not flowing in the engine (due to air bubbles, I suppose) causing a small overheating. As you removed your engine, this could also be your problem.

I drained/re-filled/purged again the water circuit and since then it's flying again.

I had exactly the same behaviour a couple of months ago, after the winter.
Engine pushing as expected until it's hot, and then it runs poorly after 8000 t/min.
In fact I didn't purge the water circuit correctly, the water was not flowing in the engine (due to air bubbles, I suppose) causing a small overheating. As you removed your engine, this could also be your problem.

I drained/re-filled/purged again the water circuit and since then it's flying again.

As soon as I started reading it I suspected regulator/rectifier as they can be temperamental, especially when hot. Do you have good airflow around your reg/rec or a good heatsink?

Phil

Cheers blume, I'll try the water thing again - doesn't cost anything so got to be worth a go

Phil, as for the regulator/rectifier - would that affect the running of the engine? I did replace mine a few years ago with one of the more solid superdream units. It's not in great airflow (passenger footwell) but is mounted on a decent chunk of metal with thermal compound as a heat sink. But this would only affect charging not running wouldn't it? I could in theory disconnect the reg/rec altogether (the 3 yellow wires from the alternator) and it should run happily, until the battery goes flat. Or have I got that wrong?

One of the functions of the regulator/rectifier is to recharge and maintain voltage for the battery after initial starting but the reg/rec also provides a constant voltage for the electrical system. When the reg/rec overheats, the voltage can spike and cause issues with running. From memory, the Honda manual has details of how to check if the reg/rec is operating correctly/efficiently?

It's been a few years since we had our blade engine Indy (about 9 years )

Phil

Ah ok makes sense. I recall testing some resistances on my old reg.

I guess as a test I could run it until it misbehaves, disconnect the alternator and go for another quick blast. That would be running from clean battery leccy only and rule it in or out. Provided I don't go too long and flatten the battery

I have (had) the same issues, in the past it was very apparent with warm weather. 25+ C. Plus after driving it for 2 hours the car wouldn't start again, only after letting it cool down for 20 minutes or so.

A few weeks ago I fitted some other coils and cleaned up all the wiring. It seems faultless now, but i haven't driven it in very warm weather yet to be certain.

Could anyone tell me if the coil mounting points need to be connected to ground?, I've had a look in the workshop manual but still couldn't figure it out. I cleaned up the mounting points, but that might have been for nothing.

I had also replaced the rectifier for one from a new model fireblde, but that didn't solve it.


If you manage to resolve your probs please let me know.

[Edited on 18/5/13 by kip]

So, further to the above. I've fixed the issue of not revving to the red line - new plugs and a second carb clean fixed that (suspect it was the plugs - carbs aren't visibly dirty). Still got the hot tickover issue though.

I've also ruled out fuel supply (filter and pump) by disconnecting power from the pump. It continues to run on what's left in the fuel lines and float bowls with the same symptoms.

I've also ruled out I think the reg/rec, but disconnecting the alternator altogether from it so it's not getting an AC feed and just running off the battery.

I've ruled out coil packs too, as per: -

* This here link

...but after a blat tonight it's still ticking over badly when warm. Basically misses a beat periodically. I've done a recording of it on the drive here: -

* This here MP3 file

Any ideas what else it could be, I'm starting to run out of ideas.

Cheers


Simon

Some trivial things that I would check for:

Bad engine earth
Air leak between the carbs and engine (split rubber)
Knackered TPS

Also does it have the pink immobiliser wire that needs the resistor to fool it? If it does it might be worth checking.

Hi guys, I've got something similar - 1997 fireball in an Indy. Been off the road over a year so changed fuel, filter and cleaned carbs.

Basically starts really well, can rev and sounds smooth through the band, once getting warm though after around 3 mins, still ticking over fine, as soon as you give any throttle, even applying slowly it goes to cut out, like a massive stall.

I thought cleaning the carbs and jets, changing fuel etc would sort it.

Seems temp related though and now considering the coils - any thoughts?

My father in law has this problem too, it was also discussed not long ago

Someone suggested then that there was a lack of air flow causing the engine to overheat and I believe 'boil' the fuel in the carbs, I cant remember the exact details though.

cheers - I actually found the faulty last weekend. In the end it was the Ignition control module - I think this had beed breaking down for some time.

It created a total failure on the ignition. When you turned it off and on again, (5 seconds) - it started and revved fine for around 10 seconds then the same thing happened again, wouldn't allow any throttle increase at all.

Changed with a space ICM I bought off e-bay a while ago and it worked fine!!!

thanks again