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Discussion Starter · #1 ·
A previous owner said to me in passing... I have it set up rich 'cos I am in QLD and ,as you know "fuel is cool".
I put everything back to stock (apart from the big pipes) and ran it like that, Fouling plugs a bit here and there.

TODAY I poked a colourtune into it and it showed yellow flame in both cylinders from 1/3 to 2/3 throttle. I
SO... I pulled the needles out only to find the needle was already at its leanest (top clip position).
I then removed the air filters and reassembled the airboxes without them. Still yellow. Any ideas? I couldn't find any markings on the needles. The only thing I can think of is he put richer tapered needles on it. Are they available, and if so how do I identify my current ones?

cheers
derek

ps I changed the head bearings today and it is like I am riding a new bike. Amazing what you can get used to.
 

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What size jets are you running? Also what pipes and airfilters?
The OIF T120Rs should have 180 jets as standard or 190s (as per the pre OIF)if you've ditched the standard filters and pipes.

Good Luck

Webby
 

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Delrazor,

Well I would say to get a little more imput on this question.
What carburator are you running? Stock Amal, or did the
previous owner change out to something else?

Knowing that someone might be able to give you the original
jet sizeing numbers.

Pookybear
 

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Discussion Starter · #6 ·
Thanks folks.
- yes the air screw is the easy bit.can watch the flame turn from yellow to blue as it turns.

- 190 main jets
- stock needle jets
- stock amals - 930
- had stock air filters (old and dirty) that I removed as per my first post.
- stock airboxes
- the pipes are unknown. loud. thicker at the header, with the old school 'sausage' part. I would have thought that if anything that would lean the situation out. I would be very nervous putting a leaner main jet in these things.

All the yellow flame is coming from 1/3 throttle to 3/4 throttle. It is nerve racking going full throttle stationary with the colourtune in, but it seemed to blue out briefly before I bottled it.

So far I reckon the possibilities are...
- plewseys float height theory
- my 'wrong needle' theory

thats all I can think of really.

derek
 

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Hi delrazor this might help you, unless you are flat out and it is weak the main jet is probably ok, you should be working on the slide and needle 3rd and 4th positions below. the float hight will effect the mixture across the full range.

it is possible and allowable to have different size jets in each carb as long as the mixture is correct. In the past I have filed the cutaway, to get the mix right with lots of plug chops in between.
 

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Discussion Starter · #8 ·
Thanks fellas.
I have ridden the bike for a couple of days with the filter elements removed and it goes way better. Still a bit rich, but leaves me with a dilemma.

- buy new air filter elements and make it even richer
- remove the whole airbox and put pods on (looks cool, but I am not rure if they allow more air flow)
- keep riding and take any risks involved in riding with no elements.

derek
 

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Discussion Starter · #10 ·
Thanks again fellas.
This morming while my 1YO slept I checked the float height. It was about .8-1mm by the technique here http://www.jba.bc.ca/Bushmans%20Carb%20Tuning.html#SYNCHRO

I have prepared an order for the 3.5 slide, air filters and 105 needle jets but will hold off to see what the float thing does.

I started it and it runs nicely now, so I must go for a blat. The baby has woken up (as well as every other living creature in my neighbourhood) thanks to the crazy pipes on this thing.

derek
 

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"The baby has woken up (as well as every other living creature in my neighbourhood) thanks to the crazy pipes on this thing."

Reminds me of "The fastest Indian" :D
"Bert, what the hell do you think you`re doing?"
 

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Discussion Starter · #12 ·
ok to sum, up the story so far.
- stock everything except loud old pipes. carb needle set to lean.
- air filter elements removed - still showing rich with colourtune.
reset float heights (they were too high by over 1mm). A little improvement but still fouling and misfiring, especially when not fully warmed up.
- plugs look less sooty but stilt sooty. Frightened the whole district coming home from my bar at 2am last night with some pretty bad backfiring . 5 degrees celcius and not warmed up. MAnaged to ride out the storm by keeping the revs up and not dropping the throttle below 1/3 open.

- After setting the float heights, the tickling became 3-4 seconds on the right and 1 second on the left. so.....
today i watched plewsys videos on carb rebuild and got into it again, discovering the following....

when testing the float height it was 2mm too high again. That can't be. Oh yes it can. I was pushing down on the tab as per instructions on one side, unaware that the tab was twisted, allowing the float to be correct when testing on one side, yet way out on the other. THE POINT i hear you ask.

ok... we move the seat up and down as the bowl tabs have a 'memory' and will bend back. Does this mean now that I have twisted the tabs to be parallel to each other, they will go back to being twisted?

Also If I decide to go to a dyno place, what spare stuff should I take?
I am thinking leaner slide, old airfilters, pancake airfilters that I want to use, 105 needle jets.

derek
 

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Hi delrazor
Have you attempted to bend the tabs on the floats?...
You should put the floats on a flat surface the right way up, and point the tang's towards each other and compare the heights, they should be about equal (a pic in this position would be handy).
When checking the float level in the bowl you can also put the gasket on and hold the bowl upside down and judge the gap by eye.
 

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Del, I think you may be pushing too hard on the tabs.
This is a dry test to simulate wet conditions,
What we are looking for is the float-level
when the underside of the tangs are just pressing on the lower part of the needle slot,
making sure that the pivot bar is in correctly.
(This is why pressing on the needle gives a slot length error).

If you are aware of this stuff above, please dont think I`m insulting your intelligence.:)

Before thinking about a dyno-run, it is essential to get the engine ticking-over correctly IMHO.
 

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Discussion Starter · #15 ·
thanks caulky,
I kinda think I got the tangs right (minimal pressure etc.) .
I am not overly concerned about the precise richness. I am more fed-up with the popping and backfiring when backing the throttle off to 1/4 open. Almost as if it is super lean at one point in there.

One other thing is when using the colourtune at various throttle positions there is intermittent really white flashes in there. I wondered if it was bits of dust exploding (or piston crown) as I have no air filters on at the moment...or something even more sinister.

Anyone out there had a go of the colourtune and seenthe 'flashes'?
 

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I am more fed-up with the popping and backfiring when backing the throttle off to 1/4 open. Almost as if it is super lean at one point in there.
Anyone out there had a go of the colourtune and seenthe 'flashes'?
Popping and backfiring symptom, says to me you have a weak mixture on the needle, I would lift the needle 1 notch, and try again.
Don't ever over rev the motor with no load on it.
I have a colour tune and used it now and again, you will notice when you turn the throttle the flash will go bright orange then should settle to blue. Apart from tick over and very small throttle opening, they cannot be used unless you have a rolling road!
Plug chops are the way to go with these old ladies.

edit:- if the backfiring is from the exhausts you should be looking for leaks around the stubs and silencer joint.
 

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It is not entirely clear where and when the backfiring and popping occurs. If it occurs out the exhaust when you are letting up on the throttle, air is leaking into the exhaust as described by Plewsy. You'll need to seal the pipes especially at the head.
 

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Discussion Starter · #18 ·
excellent news. Seems easier to seal a pipe than solve carby puzzles.
Definitely out the pipe. If I start it now and give it 1/3 to 1/2 throttle after a minute of warming up it will be like shot guns coming out of the exhaust. Hard to sneak away from the house in the morning.

cheers
derek
 

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Which House

I get your point: There is a big difference if it's your wife's house your sneaking away from in the morning or your mistress...
 

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Discussion Starter · #20 · (Edited)
no mate, nothing that exciting. Sleeping baby.
Today I rode to work and one plug failed completely (I had a spare) and the other popped and carried on.
I have sealed up the pipes, rechecked the floats, checked the needles for genuineness (NEW WORD?) and replaced the spark plugs with iridium. I'll see if it is purely a fouling issue in a minute when I attempt riding home in the rain.

On a naive side note, running on one cylinder is not quite as nice as riding a 325cc bike. ;)

derek


Update: 6 mile ride home all was well until about 500metres to go. Then the same symptoms. Either I can foul an iridium plug in ten minutes, or there is something else breaking down on the bike. I just don't understand why all would be well for a while each time I replace the plugs if it wasn't a fuel fouling issue. (always a dry chalky blackness).

getting frustrated,
derek
 
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