Triumph Rat Motorcycle Forums banner

1 - 20 of 43 Posts

·
Registered
Joined
·
26 Posts
Discussion Starter #1
My 900 sport has a fault which i can not pinpoint, i have has some improvement but not cured it.
when not under load but warm my bike will rev past 4500, but when riding it starts to splutter and pop as soon as i get to 4200 4500 this varies slightly. and if i hold it at 4500 5000 it will not go any higher. i suspect igniter cdi, but not sure and its an expensive item just to buy and find its not at fault. mu thunderbird 900 sport is a 99 model, the igniter looks like it has been replaced at some point ,Its the type that can be opened ,and the pcb removed. i read some where that heating the main plug spikes up and melting the solder on the pcb can eliminate a dry joint,which i have done to no avail.
 

·
Registered
Joined
·
291 Posts
Just a stab in the dark here but maybe the ignition advance isn't set correctly for the higher RPMs. Is it possible to connect a computer to the CDI and confirm what you have for advance settings?

Noel
 

·
Registered
Joined
·
26 Posts
It could be the ECU but unlikely.
It is classic blocked or poorly set-up carb behavour. 4000RPM about is where your main jet takes control from the pilot system.
Have you changed the pie or cans?
Have you modified the airbox or changed the filter?
Has the bike been standing for a long time?
When this happens does applying the choke help?

Good luck
 

·
Registered
Joined
·
26 Posts
Discussion Starter #5 (Edited)
igniter or not

I have taken the carbs off stripped and cleaned them, fitted new pilot screws float stop pins taken the jets out and cleaned them with carb cleaner and compressed air, all jets and emulsion tubes where clear, the diaphragms all looked good , but maybe i need to take them out again and check against a light, the air box is standard and good , it has had a new filter. it revs out ok when not being ridden and just warmed up.I tried pulling the choke when running at 4500 and it just seems to die slightly ,I would have expected an improvement if it was struggling for fuel.
 

·
Registered
Joined
·
291 Posts
Its pre ecu Noel so no means of connecting the cdi, its pre programmed as are all cdi,s
Ah I see. Sorry I made an assumption that it was an aftermarket type programmable ECU (Ignitech, etc.). In that case, maybe the coils are acting up. If they are the original coils, they are 20 years old now with a lot of exposure to the elements/engine heat. Perhaps a new set would clear up the issue (it's good to have a spare set on hand as well even if that isn't the issue at the moment). :)

Noel
 

·
Registered
Joined
·
26 Posts
Discussion Starter #7 (Edited)
Coils

The coils are new, Nology ones , I have managed to find another 900 sport owner that's only 10 miles away and he has agreed to test my cdi on his bike, Which is very kind of him, I will come back and let you know. many thanks for every ones time. appreciate it.
 

·
Registered
Joined
·
26 Posts
Discussion Starter #8
tested

my cdi /igniter was tested on another bike and is 100% working. so i swapped the pick up for a new one, i tested and found very little improvement other than it now the missing starts at 5000 revs not 4200, So i replaced the ht leads,Which made no difference, i did find if i hold it at 5000 revs it eventually goes beyond 5000 and up to 7000, Not really sure what to try next.
 

·
Registered
Joined
·
79 Posts
My bike kind of behaved like that when I modified the air filter and needed to rejet.
I had too much air in the mix.

But you have stock air filter sooo.....

...
BUBI 0_0

www.lamiatriumph.it
 

·
Registered
Joined
·
26 Posts
Discussion Starter #13
air box

ive just bought a new airbox,new rubbers and clips, ive stripped the old air box off ,and i an going to rig a fuel supply up and watch the slides to see whats happening.
 

·
Registered
Joined
·
26 Posts
Discussion Starter #14
update, new air box arrived as did the rubbers from carb to airbox, i noticed the new rubbers have seperate slots to allow air to the cv, the old ones do not and look quite worn, i am thinking that maybe they where hanging and blocking the cv holes, will update when i get chance to fit and test.
 

·
Registered
Joined
·
26 Posts
Discussion Starter #15
Sorry i have not been back on with a report,i have been working away and just got back, ive been and tested the bike today with no real improvement, what i have replaced.
plugs & leads
pick up
air filter box air filter and rubbers from carb to filter.
rubbers from head to carbs
the cdi has been tested on another bike and is 100% ok
its had 3 new nology coils.
i have refurbed the carbs and cleaned and blown them out with air,
the cv rubbers are original as they looked ok.
the tank has been washed out and the petcock and tee filters have been cleaned.
other than replacing the cv rubbers i am now at a loss, i get to 4000 reves and it holds back still.#
 

·
Registered
Joined
·
142 Posts
Some "Hot Rodders" like to install the "green" camshafts into these bikes in hopes of turning them into hot bikes. I've been looking everywhere on the bike trying to put it back to stock with all the airbox parts, jets, etc. It turned out to have the green camshafts in it. Just hoist the cam cover and look for green paint pen marks on the ends of your cams
 

·
Registered
Joined
·
56 Posts
Had a similar problem. Thought it might be a fuel flow problem. Replaced petcock, fuel line, and removed inline filter. Cleared it right up.
 

·
Premium Member
Joined
·
3,567 Posts
Without going back and rereading everything, can you tell me if the bike ever ran right? If so, what happened between then and when you first noticed the problem?

Have you done a fuel flow test?

Can you get more RPM down hill? Less uphill? More in a lower gear?
 

·
Registered
Joined
·
26 Posts
Discussion Starter #19
Ran right

Yes the bike did run right, this just happened one day, it felt like it was running out of fuel, i slowed down and flicked the kill switch on and off whilst still in gear, the problem disapeared or at least i thought it did, it starts up fine,and revs out without a hitch when warm stationary, but once i ride it it holds back, it revs to 4000 revs smooth and quickly,but as soon as it goes over it seems like its being held back and not revving smoothly almost like its running on 2. as soon as it stationary its fine, i read some where last night about the overflow pipe being too long and flapping caused similar problems for one chap, thought maybe i would take a look at that,Before i fitted the new airbox i ran it and revved it to check all 3 slides where lifting equally and fully, which they where,i will take a look at the overflow pipe today.
 

·
Registered
Joined
·
26 Posts
Discussion Starter #20 (Edited)
ran fine

And going down or up hill makes no difference .going back to thought it was running out of fuel i had a full tank, The fuel flows well and smooth, ive not done a percentage v time test, As i dont know how many litres per min should be.maybe i need to strip the carbs back down and go over them again, will check the overflow pipe first.
 
1 - 20 of 43 Posts
Top