Hi All, I've been riding motorcycle just for a few months and I do not have much technical knowledge regarding motorcycles. But I think my Triumph Thunderbird 900 Sport yr 2000 is not really okay. It chokes, rides quite unsteady, unstable below ca. 3000 rpm, but it rides smoothly above that. It also drives well if the choke lever is on and it does not matter that the engine is hot or not. The mechanic made diagnostics and found everything within specified limits. Any idea what could be wrong? Thanks in advance.
Welcome to the forum! There are some things that you can't really 'check' with a cursory exam. As a starting point, I would strongly recommend trying some Lucas Fuel Treatment. It's good for injectors and carbs, and it's a low cost thing to try. I've had some amazing results in the past.
Your description resembles my '97 Tbird's behaviour after last winter's storage. The ethanol in the 95 octane petrol had gummed up the idle jets. Emptying the tank and a 10 km ride with ethanol free 98 octane cured it. Ethanol mixed fuel does not store well.
It may be a blockage in the pilot jets,I agree on the fuel treatment, any of them for cleaning the system will help, I run redex in my 900 Sprint which is virtually the same engine, also I believe Seafoam to be good too but it depends what is available as I note that you are in Hungary. In my experience, these engines are a bit unstable below 3000 or so revs, I would guess coz of wear and tear on the jets, rubbers etc and replacing these is an expensive job Couple of things to look at, You will probably find your air filter is blocked and dirty, renew it. Your choke, you say it runs with it on or not. My Sprint will not run cleanly if the choke is still on after a minute at the most, I would check to see if the choke is fully off, on my bike you can get to the choke from under the tank, there is a small lever there, dont know if its the same on yours though, if it is turn the choke both ways and see if the lever on carbs is moving or not. My bike has a long tube running from the engine which exits down by the rear sprocket, it should have a bung in it which you have to empty from time to time,this bung was missing on mine and I put a screw in to block the tube off, it made my tickover and slow running much better, a tip I found some time back.
I'm also just a year and a half into biking and have a TBS! Mine also is a bit lumpy (and sounds like a bag of nails) below 3k. I've just accepted it as "character". I do, however, find that 98 octane fuel helps, put that could just be a placebo. There's a lot of opinions on the benefits of higher octane fuel. Not heard about blocking the pipe from the engine before, I'll give that a try.
Hi Gabor, first of all welcome to the Triumph Asylum !! Now about this 'problem' - are you sure it's really something wrong and not just the fact that you are new to motorbikes and not used to how they run ? Bikes in general run at much higher revs than car engines and it may be this which is strange to you ? One thing is for sure, you should not be putting the choke on, once the bike is warmed up.
Being a van driver, I'm used to plodding around at low revs. My DAS instructor could tell, by the way I was riding the bike, that I drove a van!
Thanks everyone for the hints. I'm going to try all these and also discuss them with my mechanic. There is one more thing that may reflect the problem. While I am waiting at a red light and the gear is in natural the rpm is around 1500 and a few times it drops to ca 800. It happens three, four times a minute. To a feedback above: I'm almost sure something is not okay with the bike. I know riding it different from driving a car but I had a gs500 before and I tried a Bandit and a Fazer a few times. I know they're different types with different way of riding and characteristics but still I think it's not normal what's happening to her. Thank you Guys for your help. I really appreciate your hints.
well after having a new air filter and running redex every fill up plus the pipe mod I mentioned my Sprint ticks over steadily at 1000 rpm. it never used to when I first had it........still sounds like a bag of spanners tho. They all do that Sir,lol
There are a number of possible causes but on a bike of this age I would be removing the carbs to: remove and clean the float bowls blast the jets and galleries with a carb cleaner aerosol check the diaphragms for splits and smooth slide operation check all caps and vacuum connections for splits/perishing. Re-install and re-balance. If it has been years since this was done the chances are you have rust particles and debris in the system getting picked up erratically. At higher rpm you have the pressure differential and velocity for them to get sucked through harmlessly. The other thing I would do is run the bike in the dark with no lights and check for arcing from the HT circuit because you might have insulation issues on old leads and caps. You might equally have one spark plug breaking down.
Thanjs for replying. She has a new TB-9095 K&N Sports air filter. Nota bene, air filter box was empty when I bought her and the above phenomena were even much worse before installation. I'm going to try some fuel additives and 98 petrol as well as that pipe thing. Hope they help. I know it sounds like a bag of spanner as normal and it's fine with me however sometimes she gives sounds as well, like jumping relay (clacking noise) with quite high frequency, which does sound rather abnormal. I rode her yesterday quite a lot. She was okay when I put the gear lower to reach 3k (and a bit) rpm however I could not manage a smooth ride in town. Thank you all for your help.
So it sounds like your bike is running lean, due to too much air getting in and weakening the fuel/air mixture. If you put in a std. Triumph air filter you may find she runs just fine.
I have the thunderbird. its got over 80,000 k on the current carbs and it still idles fine and pullslike a train from 1500 rpm. Can I suggest 1/ check the little blanked off vacuum caps on the top of the carbs are present and in good condition. 2/ When you turn the choke off look at the left hand side of the carbs and push the chock operating linkage back by hand. 3/ Check the drain plug in the airbox drain pipe that comes down in front of the swing arm pivot (10mm in diameter) .4/ sorry but the carbs need to come off and the pilot jet system needs cleaning out ,do that after spraying carb cleaner over the intake rubbers whilst running to check for leaks.4/ when the carbs are out change the small filter inside the hose where it goes onto the carbs. Most important! Make sure the screwdriver for the pilot jet is an exact fit, very , very easy to ruin head. Give the screw driver a slight tap before attemting to undo. Hope that helps and welcome by the way
