Triumphrat

Shorty · 07-13-2006

Nice hot weekend coming up (over 101 F) and I got a few Bonnie projects I need to do ie. new inline gas filter and football grips (providing they arrive).
I've been talking to some HD gearheads here at the plant about my 5250 RPM horsepower and torque dip and how I would like to smooth that out as best as possible before attempting to get another dyno run.
They suggested that I get the bike up to 5250 RPM or there abouts, shut the engine off coast to a stop and inspect the plugs. Adjust shims on the needle as required until the plugs look like the bike is running too rich and then shim down a bit. Sounds logical to me realizing though that "sparkplug diagnostics" are still a guessing game, but what do you Triumph Gearheads think? Thanks in advance for your thoughts.

Shorty

Motorboy · 07-13-2006

That is the way tuners did it before the advent of O2 sensors and dynos ........It is harder to read the plugs than you might think

......Here is another trick,,,,,, if you have access to the air inlet of the carbs you can slide a blocking plate accross the Inlet slowly at the desired rpm range and feel for the engine to change as it goes rich....This is hard to do at speed and isn't all that safe to be reaching down and taking your attention off the roadway......This is more of a track only method.....

What I do is the stopwatch method.... I find a fairly level "test & Tune" section of road far away from traffic and intersections. Then I stick the bike in one gear (higher the better) and I sweep the rpm from 4 K to 6K while WFO and click the watch on at 4.5K and off at 5.5K...... Any change becomes quite clear .

cobra935o · 07-13-2006

Does around where you live have a dyno? If they do reasonably priced runs, it may be worth just taking it over to them and let em have at it, but do the work yourself as thats where it will kill you, with the labor, if they start getting into it like that!

Nathan

Shorty · 07-13-2006

Thanks for your input sofar.
Motorboy...blocking the air is a little too risky for me, but I've tried pulling the choke at 5250 to see if that made any difference (I couldn't tell). I do plan on doing it with new plugs though.
Cobra...going rate for dyno runs are between $45-60 here in Dallas. I just paid $60 a few weeks ago and have doubts about the results (my air/fuel ratio did a perfect flatline at 13.7 with max hp at 57.3 and torque at 46.6). I'm planning on going to another dealer for a second opinion but feel that I'm still a little on the lean side. Full blown dynos with assistance from them are about $230 a pop, but it's hard to find someone with carb experience...everybody is an EXPERT with EFI though :-D . Hard to believe for a place as big as this town, you'd think there would be more options.

Shorty

Paul · 07-13-2006

14.7:1 is optimum for emissions. You could enrichen a little for maximum power. 12.6-13.2 is the range generally accepted as peak power mixture.

By the way, the numbers represent the amount of air (14.7) to the amount of fuel (1) by weight.

Or about 80 boxcars of air to a gallon of fuel, if you wish.

monkeyboy · 07-13-2006

Quote:

On 2006-07-13 08:07, Motorboy wrote:

What I do is the stopwatch method.... I find a fairly level "test & Tune" section of road far away from traffic and intersections. Then I stick the bike in one gear (higher the better) and I sweep the rpm from 4 K to 6K while WFO and click the watch on at 4.5K and off at 5.5K...... Any change becomes quite clear .

WFO only tests the main jet. He seems to be worried about the needle setting.

Can we replace our needles with adjustable needles like my ATV's have?

Shorty · 07-13-2006

Here's what I'm trying to smooth-out (click on dyno graph). The flatline on the ratio makes me think that the sensors might have been clogged.

As you can see, Torque takes off like a SOB but maxes at about 3500 RPM, drops and settles at about 42 ft/lbs to the rev limiter. Power gradually increases to the dip and then takes off, That's why I'm thinking that my pilots (42) and mains (120) are doing their job and more needle work is required (they're Thruxton needles w.1-shim).

Shorty

[ This message was edited by: Shorty on 2006-07-13 11:10 ]

monkeyboy · 07-13-2006

On a dyno they hold it wide open. If that dip is at wide open throttle, it's a main jet.

Part throttle would be the needle. You would notice that during regular riding.

Any airbox mods? I have seen resonances in the intake cause stuff like that.

Shorty · 07-13-2006

monkeyboy...airbox is modified with snorkel and restrictor plate removed, polaris bellmouth installed and a unifilter. Freeflowing Sprint teardrop pipes (similar to NH Toga's).
Can't tell any difference by riding the bike and even the Dyno Technician mentioned that he couldn't tell and was quite surprised by the graph readings. Also at the time of the dyno run I had 125 Mains installed which I've since then dropped to 120's to see if it makes a difference (over the months of trial and error I've decreased the Mains from 140 by "5's" at a time to the present setup. Above 130's I couldn't hit the revlimit in 4th and barely made it in 3rd before running out of road. Now I'll hit it every time PDQ. I knew I was running too rich before for sure.
Thanks for the reply and input. I'm pretty much set up like the Jenk's bolts suggestions with similar modifications.

Shorty

monkeyboy · 07-13-2006

Usually from what I seen the Pod filters will have a dip like that on other bikes.

It's kinda strange, but I would have it rechecked. Run it again and see what it does.