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Surging at 110kph
#32769 01/04/2006 10:40 PM
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Hope someone can help.
Gutted air box of all 3 snorkles. Then in the plastic barrier that separates the filter chamber from the rear chamber (the barrier some people completely cut out (TRIUMPHANT for example)) I cut a neat 70m hole between the two holes where the carby snorkles were.
I uprated the main jet to 130, then tried to tune it by checking plug condition. 3.75 turns out.
I had a surge at 90 to 120kph. BUT managed to tune MOST of that out by installing TBS needles. I still have a surge that comes and goes between 110 and 120kph. It can be bloody annoying when trying to maintain speed while riding with mates. Also when trying to pass trucks, as when you crack open the throttle there's this horrible hessitation.
In a straight line drag from first to top gear (to 140kph and beyond!) it absolutely gallops! I love that bit, but this surging is a worry, and takes a chunk of enjoyment out of riding.
The only other mod I performed was the 7/64ths hole enlargement of the vacuum slides.
I'm worried this is the problem as it's so far the only mod that is not reversible without big expense.
Are the slides "fluttering" at this speed / air throughput, and giving me the problem? Could it be excessive pressure / flow fluctuation due to turbulance in the box caused by the hole between the two others where the carb snorkles were?
Please help?
Regards
Michael888


Aussies have got.....BUNDY RUM!!
Re: Surging at 110kph
michael888 #32770 01/04/2006 11:10 PM
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Big Bore
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Are your throttle position sensor wires on? Possibly loose/corroded connections?


"Never underestimate the power of human stupidity" - Robert Heinlein
Re: Surging at 110kph
michael888 #32771 01/05/2006 1:22 AM
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I've never really looked at the separator in the airbox, my 03 TA didn't have the 2 rubber bits in there so I just pulled the main snorkel...
But.. if you drilled a clean 70mm hole in there, try putting a plastic plug or a button plug in that hole and see if the problem goes away. That's about the only mod you have done that varies from what a lot of us have done. There may be turbulence affecting the fuel/air mix.
Synching your carbs might help also, if you haven't done that yet.


More flags More fun!
Re: Surging at 110kph
michael888 #32772 01/05/2006 3:15 AM
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Slow Down!!! Is 110 kph fast? Or is that like 70 mph?


Ride Safe, Dennis Triumph, it's how I live and what I ride.
Re: Surging at 110kph
michael888 #32773 01/05/2006 9:45 AM
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Surging is "usually" caused by too lean a condition at a certain throttle position. Maybe try some Thruxton needles? (I am assuming your problem is when you whack the throttle at the midrange somewhere)


A word to the wise is not necessary. It is the stupid ones who need the advice. Pat
Re: Surging at 110kph
Dinqua #32774 01/05/2006 10:36 AM
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Question....have you removed your AI?
If not, you could have a bad or sticking reed valve in there.
Also check your vacuum caps on the intake manifolds and carbs.

Any type of vacuum leak can cause a "surge" and uneven throttle response.


Tony G '03 America
Re: Surging at 110kph
TonyG #32775 01/06/2006 12:40 AM
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3/4 Throttle
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"Surging is "usually" caused by too lean a condition at a certain throttle position. Maybe try some Thruxton needles? (I am assuming your problem is when you whack the throttle at the midrange somewhere)"

Absolutely!

The only other cause may be seriously over-advanced spark timing, a virtual impossibility with these bikes.

Re: Surging at 110kph
michael888 #32776 01/06/2006 1:19 AM
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I have an 04 Speedmaster and did the same airbox mod as you've described in your post. I have 140 jets installed on the bike with stock needles/shim and have not drilled the vacuum holes. I have not experienced the surging you've described. I'm about 3 turns out on the screws. Hope this helps.
So perhaps the needles are the root cause of the surging? I'll defer to the experts.

BigSteve


bigsteve
Re: Surging at 110kph
bigsteve #32777 01/06/2006 2:01 AM
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Thankyou ALL for your input. Some good leads there.
I will do the following ......
1/ Disconnect, cleanup, re-connect the throttle position sensors. Go for ride and check for surge.
2/ Replace all the rubber stoppers on the inlet manifolds. Go for ride and check for surge.
3/ Balance the carbies. Go for ride and check for surge.
4/ Plug the hole in the air box barrier, and try to tune out the surge again - out on the highway with spark plug spanner and little screw driver again!
5/ Will check for balance again with hole plugged if problem still exists.

I realize now I forgot to provide details.
'02 TBA
AI removed.
Old vacuum line for AI placed between carbies (surges with and without this mod - will remove to balance carb of course)
TOR shorties
main jet 130 from manufacturer (from Honda!) As the other I had I drilled myself with a 0.3mm bit - bloody hard to get all the goodies you blokes can get so easily.
pilot jet unchanged
TBS needles.
All three snorks removed.
Uni filter - but I personally believe they make bugger all difference except catch more dust on dirt roads - which means I do believe they are better?
OK, I have a challenging weekend ahead of me.
Thank you all very much once again.
Regards
Michael888

I think 65mph is 100kph


Aussies have got.....BUNDY RUM!!
Re: Surging at 110kph
michael888 #32778 01/06/2006 2:16 AM
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Saddle Sore
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One other thing to check.... check the clamps on both sides of the carbs and check the condition of the rubber connectors from the carbs to the back of the engine. Ok, that was 2 more things.....
The carbs move forward and back under load and if they're sucking air at these connections it could be part of the problem.


More flags More fun!
Re: Surging at 110kph
Deon #32779 01/06/2006 9:46 PM
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Thankyou, again great information!
I know it's a cruiser, made for....well........cruisin'
But for some reason we just have to MODIFY for performance!!
Thanks again.
Michael888


Aussies have got.....BUNDY RUM!!

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