Triumphrat

BritBloke · 09-17-2006

Couple related?? issues. Any help appreciated....

My 95 TB (now 9.5K) had carb problems last year (tank crud fouled the carbs). Had dealer rebuild carbs end of last season. Beginning of this season noticed intermittent black smoke mainly when I flick the throttle from idle up to around 5K, and on deceleration from high revs. Does NOT happen every time. Carbs were balanced and mixture leaned out a bit this year. All stock except screws now 2.5 turns out. Lost some umph in mid range and roll on, and is rough around town in the 2-3k range with flat spot around 2700. Seems fine when cruising 55-85mph. (Before I had the carbs recuilt, it had white smoke and blue pipes).

Second issue: Bike has idled well at 1K but this weekend started to vary on occasion with a drop to 600 or a slight increase to 1100. Has not done this before and does not do it all the time. Coil? Carb crud again?

I must admit to getting tired of this constant battle with the carbs especially as they are a PITA to work on. I have recently replaced spark plugs, battery, and installed a replacement horn with a relay. I just want my bike to work as the Triumph gods intended, not constipated like it's been for the past 4k miles. Hate to take it back to the dealer if I can fix it!!

Andy

BigVinny · 09-18-2006

I had all of these problems on my 97TB when fitted with the original Mikuni carbs after it was laid up for about 18 months when I was working abroad. Black soot would puff out of the exhausts and it would falter and stall !

I gave up in the end with the carb cleaning struggle and bought another set of nearly new Keihin CVK's off a 2001 model from eBay. Since then with a few other mods such as replacing the inlet rubbers for unrestricted ones I have not looked back. I am convinced the Keihin's are much better and more economical than the Mikunis.

The main reason for looking for second hand ones from eBay wax that a new bank of 3 costs £900 !!!!!! The ones I bought of eBay were £114 !

Good Luck !

SprintRide · 09-18-2006

replace the float bowl gaskets and the float o-rings, While in the carbs, check float height and set at 14.5mm. Re-sync and set CO to 3.0% at 1050rpm (idle). Hope this helps.

Cheers

BritBloke · 09-18-2006

bigvinny,
Thanks for this response. You didn't mention the coils, so I'll take that as a good sign...
If I could find a set of little used Keihin CVKs for a couple hundred bucks, I'd buy them! I think the problem isn't helped by peeling paint in the tank and resulting crud that makes it through the filters and into the carbs. At least, that's what happened last year - discovered this when I left the petcock open while parked in the garage and found a huge puddle of gas on the floor

If I have to keep fixing these carbs, I'm going to trade it off for something a lot more reliable. Hate to do it, but this can't be what Triumph had in mind for a modern classic, can it?!

BritBloke · 09-18-2006

sprintride,
I love specific instructions like this. Assume you did this with some success.
Much appreciated.

parrycm · 09-19-2006

How much smoke are we talking about? Any carburetted engine when suddenly revved from idle to 5,000 is going to suffer from combustion inefficiencies until the physics catches up. Check rhinoe's dyno post for fuel/air ratio ratio in the rev band, and they were probably increasing the revs gradually.

I haven't seen anyone posit a reason for the increase/decrease in revs - I'm curious as to why that happens.

FWIW, my 95 runs nicely on its Mikuni's - sorry to hear you're having this trouble.

By the way, if you are going to strip the carbs again, make sure you replace the little o-rings on the floats. They are the cause of fuel spitting back into the airbox which sometimes happens. Keyword search "carbs - lessons learned" to see my old post on that.

BigVinny · 09-19-2006

The problems I had with the carbs was due to neglect and the fact that I didnt lay the bike up properly when it was not used for long periods of time.

Im sure the same would have happened to any Jap bike with carbs in the same situation

The coils and ECU are just the originals, never had any problems there. Some of the blame has been directed towards modern fuels which contain additives which evaporate to leave the green film that is so hard to remove.

Chucktri · 09-19-2006

I've had my 96 T-bird worked on by 2 different dealers and it still blows out black smoke, gets terrible gas mileage and does not produce the power that it should. I am going to start looking around for new (used) carbs soon. I've just managed to put 1000 miles on it since I bought it 3 years ago.

Is there some thing that identifies the restrictive carb rubbers vs. the non restrictive rubbers.

Chuck Contrino
Pres. Tri-State Norton Riders

parrycm · 09-19-2006

Basically the restricted rubbers have a narrower bore or throat - you can tell by looking down them - there's a noticeable lip but obviously that's off the bike.

When mounted, I think you will find a dimple or dimples in the circumference - run your finger round them. I think this is designed to prevent you taking a craft knife and cutting away the restriction.

Got pics of your Nortons? Having two is just greedy! :razz:

Crusader3020 · 09-19-2006

Hi Britbloke

this may be stating the obvious but have you checked the fuel filter at the carbys. remove the fuel line at the carbys and it sits inside the inlet thingy - if this is blocked it is going to run like a dog