VTR Down Under

[Twitchy]

Recommend you don't spend too much money on this, I made a large airbox and dyno'd it, no gains....

Interesting.... I wonder what the post filter airbox capacity of the RC51 is then? They seem to run alright

[tony.mon]

I haven't measured it but it's not visibly much bigger, if any bigger at all.
But the SP breathes straight in through the headstock so is much more efficient, and there will be better airbox pressure at speed.

The interesting difference is the exhaust port, smaller and d shaped instead of round, with a flat at the bottom.
The pipe is round, though, so you get a step at the transition between port and header.

When I was playing with my storm engines I bought a scrap SP1 engine just to have a poke round.

[Twitchy]

A bit of a callout to Mik_str if possible. I have been mucking around with the jetting after installing the fuel pump and not sure how far to go.

First, when I bought the velocity stacks from HPower, Bill suggested going down 2 on the mains, which took me to FP 172 front & 175 rear. I have removed the high mount Jardines, and working on a Mori titanium system with Akra cans. Because I am not finished with the exhaust, the old exhaust seals are still in the head, so I may have a slight leak there. Apparently low mounts require smaller mains and larger pilots from high mount systems. Not wanting to run too lean at high rpms, I went down 1 main size, to 175 & 178, and went up 1 pilot to 50 f&r. Absolutely stank my shed out it was so friggin rich. I could shut the front screw completely and it did not affect the idle, winding the rear screw in increased the idle quite a bit. So that means the pilots are too big right?

Today I have put the 48s back in, and dropped down to Bill's recommendation of 2 mains lower (before the stacks I ran 178 & 180), mains at 172 & 175. Ended up with the screws out 3 1/8 and 3 1/4 f&r, but still getting a hang up at 2200. And when I blip it to 4k, it is not the clean snap it used to be (full throttle blip easy with HRC throttle tube), it feels flat, which tells me its too rich still. With the (apparent) lean situation causing the hang up, I know each circuit affects the others, would the mains affect the fuel screw, idle and blipping? I am considering going down on the mains again, to 170 and 172.

So my question for Mik is(or anyone for that matter), with fuel pump, how many mains should I go down? I am concerned if I go too low, when I take it for a spin, she will run way too lean up top. If the stacks require dropping the mains by 2, the low mount exhaust requires 1 size lower, and maybe the pump means dropping 1 size main, total 4 steps down. Seems a lot.

[tony.mon]

The more tuning you do, the smaller the mains need to be- which seems counterintuitive.
I ended up with sizes in the 160's.....
Ideally it needs setting up on a dyno, an alternative is to fit wideband lambda sensors in each downpipe with a display, which is what I did.

Another possibility is to fit main jet circuit Flo commander systems, this gives you the opportunity to "spoof" one size bigger or three sizes smaller main jets, and you adjust with a screwdriver at the side of the road in two minutes rather than having to remove the tank and airbox to change jets.
You can also get a pilot jet circuit version to get it just right.

[Twitchy]

So if I go down to a 168 front and 170 rear for example, how much will that affect the pilot circuit? The 48s with 3 1/4 turns out hangs up, but with the 50s I could close the screw and not affect the idle. Would the smaller main essentially reduce the flow of the pilot? I do realise with these carbs to start with the main and work down, but don't want to go too small on the mains and risk damage. Maybe I do need to look in to the Flo Commander...

Regarding the lambda setup, I do have an Innovate LM-2 O2 meter with 2 sensors, and the titanium bungs to weld into the front & rear pipe. The controller will go under the seat, where I can upload the graph to my laptop. I also need to wire in the analog cable to track rpms.

And bloody bugger, Jets R Us aren't shipping internationally due the dang Rona virus. Have put feelers out to a couple of Oz distributors. The 172 and 175 I have in the bike at the moment are the smallest I've got!
So now I wait on more shipping

[Twitchy]

So I have a Flo Commander on the way, and I have received some smaller main jets. Installed 168 front, 170 rear, 50 pilots, screws 1.5 front and 1.75 rear. Still getting massive hangup when blipping it to 5k, like 5-10 second hangup. Haven't wound the screws out as I ran out of time, balance is all but spot on.

But, I haven't finished off the exhaust yet, so the used copper gaskets are still in the heads, and the old seal in the rear cylinder down pipe. Not sure how much those unsealed points would be affecting the result, but will get those sorted, and take it out for a squirt.

[tony.mon]

My prediction: 50 pilots will still be too big.
You can't do any damage with smaller mains for short test rides, just don't labour the engine uphill in a high gear, as long as it isn't pinking.

Exhaust gaskets shouldn't make much difference, except it will pop and bang on the overrun if there's a leak.

[freeridenick]

My recommendation is spend the money on a Dyno guy. Four hours and and couple of hundred quid later and my bike was sorted. Would have taken me weeks otherwise and I'd have paid double by then if someone had said I could have sorted that for you.

Like Tony said, more mods means smaller main jets. In an earlier post you asked how many jets to go down with the fuel pump fitted. The pump won't make a difference to fueling it just stops fuel starvation on long fast corners on the track.

[Twitchy]

One thing I did omit in my previous post, when blipping thew throttle, there is a delay/resistance to rev. It doesn't pick up the revs quickly, there is a hesitation there, which I thought was a sign of being too rich. But it did it with the 48 pilots in as well. With the excessive hangup, it has me a bit puzzled. But this is all part of the process right? Sometimes it p!sses me off, but most of the time I enjoy it!

Regarding the dyno Nick, at $110 a run, I try and minimise any dyno time. I am not paying a guy to dyno, rejet, dyno etc. Which is why I got the Innovate system, to reduce dyno reliance. I just need to get it fitted...

Trying to cover too many bases at once never seems to work out.

[Twitchy]

My prediction: 50 pilots will still be too big.

So I went from a 168/170 main to a 170/172, but left the pilots at 50. Screws set at 1.5 turns and 1.75 turns f/r. Bike started quite nicely, warmed up etc. As soon as I wound the screw in half a turn, the revs increased a LOT, like 500 rpm at least. Shut the screw completely, the bike kept running. Ditto with the rear. As soon as I wound it in half a turn, revs shot up. So it looks like you were spot on Tony, 48s going back in this weekend.

But... the revs still don't want to snap when I blip it. Doesn't really stink of being too rich, something is holding it back. Just a though, how much effect does the slide have when blipping in the driveway? Will a 1 hole slide (slow to open) affect the speed at which the revs rise?

Just trying to get it halfway rideable before I take it out for a squirt.

[Twitchy]

So I dragged out my spare slides which I had blocked up 1 hole, and wanted to drill a second hole 3/4 size. Which I did using the Dynojet drill guide. Upon closer inspection;



Yeah so now I need to source another set of slides.

Anyhoo, popped the 48 pilots in, and gave it a crank. Was real difficult to start. Got it going eventually, kept the idle up to around 2k to get it warmed up nicely (needed the thermostat to pop to bleed off the cooling system chock full of new Water Wetter/distilled water). Faffed about for a while, still didn't want to snap to 4k when blipping. Oh and guess what?? The front screw was shut.....

So... running 170/172 mains, 48 pilots, screws at 2 and a bit front and 2.5 and a bit rear. Slides with 1 hole, DJ springs. Hoping the DJ springs will help the slides open quicker to offset the single lift hole. It now idles nice at 1200, snaps real nice to 4k with a full fist blip. Feeling pretty good about it.

Next steps are put the front end back (fairing) back on, take it for a squirt to my welder guy, get the 02 sensor bungs welded in, and I can get the Innovate LM-2 up and running. Hopefully the Flo Commander will be here soon which will help.

And a big thanks to mik-str, sirch, tony.mon, cybercarl, 8541Hawk and many others for documenting your process here and SH forum. Inspiration, and the highly contagious OCMD have led me to this point. Once I get this lot sorted, I have Carrillo rods, stainless valves and upcoming pistons to play with.

Sometimes my posts on here are just spilling thoughts and may come across as ramble, but its my thoughts, and me working through what I have done in my own head. Thanks for your patience

[tony.mon]

I do the same thing sometimes, and also find spilling it out on here helps to clarify my thinking.
Sometimes I don't even hit submit, as I've answered my own question putting it into print.
But it's always interesting to see what other owners think, especially with untried ideas.

Sounds like you're nearly there, but it's interesting seeing af ratios in real time as you ride, to see how close you got.

[sirch345]

So... running 170/172 mains, 48 pilots, screws at 2 and a bit front and 2.5 and a bit rear. Slides with 1 hole, DJ springs. Hoping the DJ springs will help the slides open quicker to offset the single lift hole. It now idles nice at 1200, snaps real nice to 4k with a full fist blip. Feeling pretty good about it.

That is sounding much better, it looks like your are getting there, so well done with your perseverance

I do the same thing sometimes, and also find spilling it out on here helps to clarify my thinking.
Sometimes I don't even hit submit, as I've answered my own question putting it into print.
But it's always interesting to see what other owners think, especially with untried ideas.

Couldn't agree more

Sounds like you're nearly there, but it's interesting seeing af ratios in real time as you ride, to see how close you got.

It will be interesting to hear how close you got

Chris.