Dissapointing Dyno run

[striderider]

1st poster, long-time lurker:

I've recently got my NTV 600 back on the road after being SORN for 18months (new Avon tyres, K&N filters, NGK iridium plugs, fully synthetic fluids, pads, battery, etc basically all the usual consumables have been replaced).

I also had a custom, stainless, straight-through exhaust (with internal baffles) made. see pic:



I recently took it to "Tim Blakemore Racing" in Bristol for a Dyno run/carb balance to get it all running nice. (excellent service and a wealth of knowledge, full of suggestions and advice).

After a few Dyno runs and a few tweeks & adjustments my 19 year old (UK Spec) NTV 600 Revere has a total of.....

wait for it......


......on the edge of your seat....

....

..
......rear wheel output of...


...38.64bhp/31.33ft-lbs

To put it mildly, I was a bit miffed (not at the garage or the work they did), just disappointed that the old-girl has 'lost' so much power over the years & there's nothing shy of £300 to get some of it back. (Stage 1/2 carb' kit with a measly 5-8% bhp gain)

Out of curiosity has anyone else had a proper check at their output recently as wondered if this is what is expected?

I know these girls aren't about power & I'm fairly happy with hitting a speed faster than I should be.

I was just hopeful to be around the 50-55bhp mark - similar to factory after replacing the standard consumables with nicer stuff.

Added Dyno graph if anyone wants to know:

[Jake]

Nov 7, 2011 14:07:47 GMT -5 striderider said:

1st poster, long-time lurker:

I've recently got my NTV 600 back on the road after being SORN for 18months......
I recently took it to "Tim Blakemore Racing" in Bristol for a Dyno run/carb balance to get it all running nice. (excellent service and a wealth of knowledge, full of suggestions and advice).

After a few Dyno runs and a few tweeks & adjustments my 19 year old (UK Spec) NTV 600 Revere has a total of.....

wait for it......

...38.64bhp/31.33ft-lbs

To put it mildly, I was a bit miffed (not at the garage or the work they did), just disappointed that the old-girl has 'lost' so much power over the years & there's nothing shy of £300 to get some of it back. (Stage 1/2 carb' kit with a measly 5-8% bhp gain)

Out of curiosity has anyone else had a proper check at their output recently as wondered if this is what is expected?

Hi Striderider.... ;D

Sorry I missed this post first time round. Interesting stuff.
38bhp..... ouch. I'm definitely not tempted to get my bike tested.
Do the modified exhaust and K&N filters really help?

The only mods., I've done on my bike are synthetic fluids
and Splitfire plugs (I've tried Iridium but preferred Splitfire
which you can't get anymore).

[striderider]

I have/had no benchmark to compare without the work I've done.

I Purchased the bike 3 years ago, from eBay, unknown history. Gave it a full service upon purchase & it's been sitting outside, unused for 18 months. The collector box was shot through & thought it time to offer some TLC.

I struggled to keep up with a er6 - hence why I had it assessed.

As I've mentioned - I'm not trying to chase the horses, just wanting it back to how it should be.

This weekends work is to change the final/shaft drive oil, fit pods (give the carbs a good clean), change fuel filter.

Once I've plucked up enough courage (I'm not mechanically/technically able) then I'll look at what jets sizes I'm running & purhaps replace them with ntv 650 or deuaville carbs.

This is a budget bike, some call it a rat-matt, I call it cheap fun & a learning curve

[gills]

Very interesting fuelling graph. I wonder if change in pipes & filter is causing the rich and lean points? Part of your max power problem is likely to be the lean mixture over 7k rpm. Generally for max power you want to be running a little on the rich side (below the dashed line).

Other interesting thing is how flat the torque curve is - very flat between 3.5k to 6.5k.

[striderider]

Am I correct in thinking that it's the mainjet that controls the air/fuel at higher rev range.

I've seen people running larger mainjets, (148/143) but not 100% what effect this would have on trying to even out the air/fuel.

Re: the torque curve: I've looked at other V-twin engines torque graphs (Harley/buells) & they are very flat throughout the rev's

[gills]

It's a combination of the mainjet and the jet needle. In CV carbs there's a tapered needle which slides up and down in the main jet, depending on the demand from the engine. Have a look here: www.factorypro.com/tech/carbtun.html for a bit more info or Google CV carbs.

Flat torque curves are great for usability (i.e. engine will pull over a wide rev range), but I didn't expect it to be quite a good as that!

[maak]

www.gsparkplug.com/shop/splitfire-sf4e.html

[kev2109]

can i ask where did you go to have the pipes made and how much did they set you back??

[striderider]

The pipes were made by a local fabricator; Taking the original stainless down-pipes, cut off just before the collector box and butt-welded 8" extension piece.

Original quote was £50, but for them for £20 'cos he took a month to get round to doing them.

I've since put some 'magma-wrap' on them, so it currently looks like:

[ssray]

How did you come to the length of the pipes?
Do they have no silencing at all?
what size are they compered to std? have you a std exhaust to fit?
Cheers
Ray