Project X

[Alan H]

Let me know if you're going up & when and I might pop up with my 550A. I'd love to know what it shoves out (ported, skimmed heads, special pipes) etc.

[PaulD738]

Let me know if you're going up & when and I might pop up with my 550A. I'd love to know what it shoves out (ported, skimmed heads, special pipes) etc.

Probably less than suzuki claims for it

[Alan H]

Not that one!

[madforitkev]

Well, spent a fun day with Dave at Mutts Nutts near York.

What a great bloke and an impressive dyno!

This guys really knows his stuff and has even turbo charged a 2 stroke!

He does a lot of work with Yamahas but I won't hold that against him and he is really interested in my old Kettle.

We had a great chat, swapping EFI knowledge for dyno knowledge, so I am going up with the bike in December.

Stay tuned!!

[Alan H]

Told you he's good!

[madforitkev]

First dyno run at Mutts Nutts last week.

Had an interesting start to the day, with a frozen water pump! Coming from down South we don't do anti-freeze and why would I bother in my heated workshop? 24 hours in a sub-Artic Transit van in Weatherby told me I needed anti-freeze! Learning all the time.

It is just so simple playing with the maps and watching the power change! No smelly carbs to deal with. Dave has an awesome dyno setup and he really knows his stuff.

Seem to have fixed most of the earlier niggles and am now left with two issues.

1. My ECU's TPS signal (throttle position sensor) is a bit noisy. While some of it could be down to electrical noise, as it was random jumps it made me do some digging about how acceleration enrichment works. Basically when you crank the throttle open all bikes will run lean while the fuel catches up. With the ECU there is a acceleration enrichment function that reduces this. This feature also has a sensitivity adjustment to smooth out false signals. The system is explained here;

https://speeduino.com/wiki/index.php/Ac ... ew%20load.

I will play with this later today and let you know how it goes.

2. My clutch let go. The clutch is off a Honda RS250 race bike. I chose it (wrongly) because I looked at the BHP number for the bike (98bhp ish) and decided it was close to what I would achieve and Honda were bound to have built in some head room right? What I should have looked at was the torque (turning force) which is really what drives the clutch decision. The Honda produces 52.2Nm. A standard kettle produces 83 Nm!

So temporary fix is sling a wet clutch back in again (because I don't have room in the existing dry casing for more plates) and then work out how to graft a Ducati dry clutch in.

Slow but sure.......

[teazer]

Let me know if you're going up & when and I might pop up with my 550A. I'd love to know what it shoves out (ported, skimmed heads, special pipes) etc.

I forget what Suzuki claimed but a test back in the day made 31 at the rear wheel and 37 on a well set up example on a chassis dyno - not a rear wheel as we know them now, so that is probably slightly higher than stock. Ours made about 50 at the rear wheel from 5200 to the red line with stock ignition timing on a motor with about 2mm off the head, big ports and a decent street exhaust. Changing timing after that really let the top end free and was worth about a second over the quarter mile, so be prepared to play with timing on the dyno.

Stock GT750s seem to make about 48 rear wheel hp. I seem to recall a run that Baz posted made 51hp and another made 55, but I don't know what the changes were. I saw another chart that claimed 55hp at 6,200 rpm from Ian Sandy with pipes IIRC. He also posted one with 68HP fitted with Gibson pipes according to the notes. A third chart had 52hp pre-rebuild which seems a bit high and another line at 63 and a third with 70HP and Gibson pipes supposedly the same run on the same date as the 68hp run, so perhaps they were corrected differently.

We ran one motor on the dyno and made 76 rear wheel HP and then some years later it made a few HP less on a "tight" dyno after upgrades and again it was flat at the top until the timing was retarded more.

Jetting- or in your case Injection timing/mapping - make a difference but ignition timing become a bigger issue with a ported, piped high compression motor once you get air:fuel close to optimum. Stock bikes don't seem to mind where the timing is set, but start to improve performance and it becomes progressively more important to get it right.

[750ynot]

We live and learn

Great stuff so far!

[garry55]

Dave is a genius with 2 strokes and a great all-round guy- he used to live nearby but then moved away to Thorp Arch. Haven't been to his new gaff yet, but will be paying him a visit next year to get the Ignitech unit programmed on my TDRGV250.

[Alan H]

I'd just like to put the 550 on and see what it's doing after I built it really.