F5’s first ever brand new bike!

[F5 Dave]

Well. Doesn't time fly? I am finding myself with little spare time & motivation these days, kids seem to do that to you.

Earlier this year I spent some time messing around with ignition timing curves int eh programable ignition. Made some improvements but not huge ones.

However there is now progress. After somewhat of a wait (problems with the machinists etc) I have today received the TSS PV kit. My Op to take the plate out was in March & I sent off the barrels to have the valves fitted just before that.

I will now match the valves to clear the pistons & reassemble making sure the PV servo is still all go when I plug it back on. Then it's test time. I also have some more needles to trial.


So behold Motoporn!

[vifferman]

Noice!
I look forward with much anticipation to further instalments.

[TygerTung]

Yes, it is very nice. I also eagerly await further progress on this machine. I can't really talk though as the only time my 350 has been going in the last 3 years is when I got it going to ride it up to the ACC protest and developed an airleak in the base gasket and it has been sitting in my garage in a part disasembled state since! I must get around to putting those great pipes I got off you on it too.

[F5 Dave]

I have been wondering how those got on.

[Reckless]

Keep the reports coming Dave! Be interesting to see if you can get those carb's sorted!

[pete376403]

Have you considered fuel injection? Have got a haltech programmable unit - pretty basic but quite tuneable with a laptop. Does your engine have a charging system?

[F5 Dave]

Yeah we went over this in the last page. Don't want to throw any more variables into the mix. 2 strokes are hard to inject at the best of times.

[Reckless]

Dave is there a base you can find for the carbs, like on the net where someone else has raced or run one of these engines?
Its quite a big ask to start from scratch with emulsion tube,needle, idle, main jet sizes and then throw in timing as well??
We used to do all the above when using Motoplat ignitions and running methanol in our karts.
But we made adjustable power jets so we could lean the bottom more and still be ok on the main jet end of the scale for road racing.
We where where getting 43 horse out of the top 125's 10 years ago so you getting 100 horse out of this is well achievable I reckon!

The way I see it the bike should be able to run ok with a std advance and the jetting then should only have be changed richer to cure a lean situation as you advance the timing?
Be careful not to advance it to much so you get detonation and loose the front off those lovely pistons LOL!!

The only way I can see without the computer programes the manufacturers have is to plug read?
Rob Taylor used to be pretty good at it when I was Karting and we got ok at it over the years.

A trick used sometimes was to leave the main jet out till the Idle and mid was ok. But don't expect it to run over 3/4 throttle if you try this method.
Also the old benchmark of if you turn the idle air screw more than 2 1/2 turns to get decent idle you have the wrong size Idle/ pilot jet in

but I'd imagine you'd know all the above I'm not trying to tell you how to suck eggs LOL!!.

Good luck with it I don't envy your task! Your gonna have those carbs apart a few times yet I'd guess!! Good read mate!

[F5 Dave]

Yeah I run an oil tank as my petrol tank so I don't have any access issues getting to the carbs. I've run without mains to trial that. There have fixed emulsion tube in Keihin & use different thickness needles, unlike mikunis.

The bike has a fully programmable ignition so it is physically set with way too much advance & then adjusted back in software & a curve applied. I ran the std ign curve for ages & wasn't getting anywhere fast, but my french connection told me you needed to run heaps of advance with these big cylinders in the mid revs or it would splutter no matter what the jetting. Ahh.

The cylinders are 250cc rather than std 175 & like 13 ports instead of 7 so they breath completely differently through carbs twice the area.

So I've been through 5 sets of needles & matched the best mains & pilots to them. I now have been suggested some less lean needles, but perhaps with smaller pilots they may work better.

They pull 120hp in race trim (quads using this engine went 1st-2nd in Pikes peak a few yrs ago), but this is not a race bike, I want it to last. I'm not getting hung up on peak power, though it is easy when it is so close to 100. Maybe the PVs will push it over?

No no it doesn't matter.

[Reckless]

I now have been suggested some less lean needles, but perhaps with smaller pilots they may work better.

That to my thinking would lean the Idle/off idle and richen the mid? Bearing in mind the pilot is the only jet that inputs fuel right through the throttle range. So the effect might be minimal I'd guess??
Where in the throttle range is the main problem and does the plug colour show it to be rich there??

I have some good articals on plug reading and 2smoke tuning that I send to the off road boys if you want to PM me your email.
Thats about as much input as I can suggest over the internet when it comes to tuning?
You may already know far more and have more expertise than is in them but I thought I'd offer.
I love this stuff even though I'm not as good as some at it, I wish I was still in Wgtn! LOL!!

[F5 Dave]

It is just spooging a whole heap. I've cleaned up throttle response a lot from the start with the leaner needles. The needles also can flow at idle if the diameter is too small. The gas released though the needle jet is large drips at low airflow whereas the pilot jet cct is higher velocity & can deliver better atomised fuel. With my GasGas I went down in pilot till it ran better, but was still a bit stumbly. When fitting the LTR kit needle which was leaner when throttle closed I had to go up in pilot size & then it was sweet. I hadn't realised that the needle could flow at idle. Ideally it shouldn't, but it does if the diameter is too small.

[F5 Dave]

Was supposed to be racing yesterday but the rain put me off so didn't need much excuse to get garage bound.
Spent yesterday just tickling up the intentionally too long blades to match ex ports & shortening a cable & testing it with the YPVS servo motor. On/off/grind repeat.
All was going well. I'm even making up a plate to bolt onto the torque arms which are tied to the front of the frame; the engine twists a bit from vertical on the dyno so I am adding a side torque arm.

Only progress was thwarted by absence of a 20cent piston circlip. The only ones I had we right dia but too 1.2mm rather than 1mm wire & don't go into groove convincingly enough. I'm looking forward to trying this new set up out. Now to go find out what a 20cent circlip costs, or even if they have one (read several).

[F5 Dave]

Well two steps forward & one step back.

So I’m running the TSS powervalves & had experimented with some Viton o-rings for the heaqd seal. They were too narrow & it leaked so back to the 2.0mm std ones (poor design has them compressing too much). Another aborted trip to the dyno.


So now I try again last night. Runs up ok. Try the new CEL needles in the PWK35 carbs. Hey that’s not bad! Try some richer mains & pilots & then leaner pilots & richer mains again. Hey we’re getting somewhere. Hmm, bike won’t start.

Check plugs. Kick kick kick. Take it off the dyno (no charge to spin the drum sadly) & crash start it (easily). Put back on dyno, try to restart (doesn’t idle). Kick Kick Kick.

Grr. Crash start, take for a ride up the road & it goes quite well.

Get out voltmeter. 10.2 volts. Rev it stays the same. Great that’s just what I need! - a queer charging fault.

So back home to sulk again. This morning I pull the bike out & try with another battery & it is charging 14V ok. Duff battery. I’ve been using a small YTB4B-BS. But clearly it isn’t man enough for the Zeeltronics & might have been knackered a bit by vibration, who knows? So I walked into a free ~ std RZ size battery, just need to mount it.

Left pipe still smokes more than the right. Odd. Water level down a bit. Either it is still leaking or it pushed a bit out getting hot on the dyno. May try swapping the carbs & reedblocks over for giggles to see if the smoking swaps sides.

When I had it apart there was a lot of oily brown tar like residue in the left chamber. I convinced myself it smelt like coolant. Those o-rings did leak, but these ones should be ok from new. Is it still leaking I wonder.

Nothing’s simple huh?

[F5 Dave]

Well things have taken an interesting turn. I’ve noticed that I’ve been losing water & it appears it has been going into the cylinder on KH side. Changed 0-rings etc. Took it apart to check head & base gasket/plugs in bottom of barrels to see if it was leaking there.

Then I bolted the head on & short hoses with bungs in them & a tyre valve. Pumped it up & SSSSSS. Well there’s a leak.

Dumped it in a barrel of water. Bubble stream. Out of an invisible hole in the PV slot. Oh dear. Can’t get to that to fix it.

Ring the distributor in US I bought it from.

“Hmm June 2007” Yep it’s bean that long. “OK well send it back & we’ll fix or replace it”

So that’s pretty good service. Sadly it’s been there for a month & they have said they can’t fix so they will get me a new one. Which will be 6 weeks.

Oh well. At least I’ll have a decent chance of tuning it without water spraying in putting out the fire at low revs. Wish I’d known this 2 years back when I had it going for the first time. Funny what catches you. I never thought it would have a block leak.

Oh well there goes another summer without the 500 going.

[White trash]

You poor bugger. I guess this is one of the joys of building specials however. And better you than me. I'd just take the fucken thing to the scrappys by now.