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Old July 17th, 2022, 04:57 AM   #121
petrolhead
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Budget limitations mean I'm also the team's seamstress and electrician.
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Old July 20th, 2022, 01:48 AM   #122
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The two sets of warmers I have, were bought second hand. And they're not the most hitech to begin with.
When we get to trackside, putting them on is the first thing I do. Front goes on first and comes off last. I keep a blanket with aluminium foil on top of the front heater.
I'm not so much concerned with the surface temperature. More interested that the heating time is long enough. Rubber in itself is a heat insulator. Takes a long time for it to be hot on the inside too.

I realized that that philips head screw on the filler cap assembly is just an anti theft measure. Can't remove the assembly without out a key. I took the screw out. Now, should I ever forget the key, the bike is still operable.
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Old July 24th, 2022, 02:57 PM   #123
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Google maps link to the karting track we call our home circuit.
https://maps.app.goo.gl/HdAGKoSMujQDJKbp7

Narrow, short, twisty. Great for training riding technique. 8 metres elevation change in a small space. Reasonable run off areas, low top speeds. So I can tell my son to just go for it.

My boy's favorite, Pesämäki circuit at Honkajoki, Finland.
https://maps.app.goo.gl/Ay6z9nsbgKfQeiLj8
Just perfect for a youngster with a 250. A lot faster than a karting track, half the size of a proper racing circuit. 400 metre main straight, 5th gear.

Last futzed with by petrolhead; July 25th, 2022 at 03:57 AM.
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Old July 24th, 2022, 05:27 PM   #124
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Oooh, very nice!!! Since track-day season is over for summer-break and racing won't start up again until Sept., I've been going to PKRA weekly - https://goo.gl/maps/3zSio5kgVa2FrMtG6

However, N250 is too big for this track, I'm stuck between 1 & 2nd-gear most of time. Looking for smaller lighter (100kg max) 65-100cc 2-stroke bike. Something like Kawi KX65/85 or Honda CR85R...

Last futzed with by DannoXYZ; July 26th, 2022 at 09:37 AM.
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Old July 25th, 2022, 03:57 AM   #125
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Quote:
Originally Posted by DannoXYZ View Post
Oooh, very nice!!! Since track-day season is over for summer-break and racing won't start up again until Sept., I've been going to PKRA weekly - https://goo.gl/maps/3zSio5kgVa2FrMtG6

However, N250 is too big for this track, I'm stuck between 1 & 2nd-gear most of time. Looking for smaller lighter (100kg max) 65-100cc 2-stroke bike. Something like Kawi KX65/85 or Honda CR8R...
Closest possible gearing is the answer for karting tracks. Rev drop between 1-2 is massive. 2-3 is a lot better, noticeable everywhere.

We're currently at Pesämäki circuit. So far 3 seconds quicker than last year.
Edit: 4,7 sec improvement from last year. 3km/h higher top speed. On shorter straights almost 10 km/h faster. I'll compose a video at some point. Morning warm up plus 43 timed laps.

Last futzed with by petrolhead; July 25th, 2022 at 12:05 PM.
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Old July 26th, 2022, 05:44 AM   #126
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Link to original page on YouTube.

I could swear replacing the front warmer's power cord with a thick one with good connections made it heat up better.

I haven't got previous years' data available anymore, but jugding from videos the apex speeds were now higher and he opens the throttle earlier on exit.


Last futzed with by petrolhead; July 27th, 2022 at 01:02 AM.
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Old August 2nd, 2022, 11:51 PM   #127
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Current specs

Since I cant edit the opening post, here's a recap of the current specs:
- race fairings, DIY foam seat from a camping mattress
-Michelin Power Cup evos(110 & 140), Bstone R11s in storage
-13/48 sprockets (others in storage)
- ~0,5kg battery
-1,5kg DIY muffler v 2.0
-DIY rear sets
-tank grips
-some cheap clip ons with soft Renthal grips
-Front brake Brembo P30/34 caliper, stock disc
-Braking 16mm radial master cylinder
- ~8% quicker throttle
-about 140kg or bit less with couple liters of fuel. Nonessential wiring and most brackets deleted. Kickstand, its bracket and aux parts deleted.
-Stock suspension, bit thicker oil in forks.
-Rear wheel pushed as far forward as it can fit.
-Ignition lock deleted

Last futzed with by petrolhead; August 7th, 2022 at 09:06 AM.
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Old August 5th, 2022, 12:05 PM   #128
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I was familiarizing myself with stuff related to swapping the engine. The new motor came without clutchparts, stator etc.
Now the factory manual says the clutch outer basket needs to match the crank gear. Match color markings and choose the right part number accordingly. I'm guessing this has to do with tooth clearance between them. Does anyone have practical experience of this? I was going to swap the old clutch stuff to new engine. Thinking am I allright if I measure the tooth free play before and after and call it good if it's not very wrong.
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Old August 5th, 2022, 01:31 PM   #129
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yeah, should be OK.
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Old August 7th, 2022, 08:46 AM   #130
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The rider mentioned that the throttle travel feels long/difficult on certain spots of track. So..

14,90€ minus company discount, throttle tube with a set of cams/rings whatddoyacallem. I had previously used some 2 component plastic repair goo to get little more diameter. It was now 37mm, the new one is bit over 40mm. Not a big change but surely helps some. For some reason it took a lot of filing and sand paper to have smooth operation and return. Lot of my mods are like this. Get the cheapest solution and then spend half a day trying to make it fit and work.
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Old August 8th, 2022, 11:36 PM   #131
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Does anyone have an opinion which are better, Wiseco or JE +2mm pistons? I read somewhere that they're heavier than original? Can't find the info right now.
Edit.. JE pistons are apparently 140-148 grams. Other info still appreciated, including the weight of originals.

Last futzed with by petrolhead; August 9th, 2022 at 02:42 AM.
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Old August 9th, 2022, 08:47 AM   #132
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Both heavier than stock.

Check with Spears Racing for upgrade parts. He's been most helpful to me over the years.

Budget builds can use even better parts. +4 +5mm over using ZX-6R cylinders and pistons. Buy used on ebay for $20-30. Press out factory cylinders, machine block for ZX-6R cylinders, install pistons, done!

Look up bruce71198's builds. He's gotten double factory power.
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Old August 9th, 2022, 11:50 AM   #133
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Quote:
Originally Posted by DannoXYZ View Post
Both heavier than stock.

Check with Spears Racing for upgrade parts. He's been most helpful to me over the years.

Budget builds can use even better parts. +4 +5mm over using ZX-6R cylinders and pistons. Buy used on ebay for $20-30. Press out factory cylinders, machine block for ZX-6R cylinders, install pistons, done!

Look up bruce71198's builds. He's gotten double factory power.
I'm not looking for the very last hp and cost be damned. Nor am I ready yet to start hunting the last possible cc:s from this engine. My calculator says the engine makes 20,7 Nm @ peak power revs, 11000. 25 Nm is possible, 24Nm is feasible with 249cc. I'm interested in making a bit more torque a bit higher up the rev range. 40hp engine power is doable without over bore. I'm just asking for experiences different pistons should I go that route. I consider piston weight to be critical for the longevity of rods and bearings. Bigger bore would mean a Cometic head gasket, which are not without issues.

If I open up the engine and find that the cylinders and pistons are in top condition, I won't replace them just for the hell of it. Then I'll concentrate on the top end.
Spears. They'd be one mighty expensive set of jugs once they reach me. Add VAT, postage and customs to their price tag. I don't doubt their quality.

Last futzed with by petrolhead; August 9th, 2022 at 01:24 PM.
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Old August 19th, 2022, 04:06 AM   #134
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What kind of engine power or RWHP have people gotten with the stock ITBs, which are 28mm? I'm not completely sure whether they'll be a restriction.
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Old August 19th, 2022, 03:12 PM   #135
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I've gotten 32-33rwhp with factory carbs +24%. They're not much restriction. Main restriction is intake-ports inside head. Compare 250 head with 300 head and you'll major differences.
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Old August 20th, 2022, 12:07 AM   #136
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Quote:
Originally Posted by DannoXYZ View Post
I've gotten 32-33rwhp with factory carbs +24%. They're not much restriction. Main restriction is intake-ports inside head. Compare 250 head with 300 head and you'll major differences.
You are talking about carburetor which I undestand are 30mm a piece. Injection ITBs are 28mm. Difference in cross sectional area is (30/28)² , right? That's almost 15% more.

Edit. We were at the Akaa track again today. He got to ride behind a much faster supermoto, improved his lap time quite a bit. He seemed to think the "new" tyres have much less slip. I lowered the hot pressures some, no ill effect. I've kept fairly conservative (high) pressures on them until now.

Some repeating gear shifting problem between 3 and 4. We do have the spare engine package, should solve that problem. The quicker throttle was a noticeable improvement the rider reported. I was skeptical whether it would help since the change is small. No complaints about the shortened foot pegs.

Last futzed with by petrolhead; August 20th, 2022 at 10:39 AM.
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Old August 20th, 2022, 01:55 PM   #137
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EFI 250 ends up with +5bhp more than carby models for same mods due to ability to precisely adjust fuel-maps ~36rwhp. I doubt TB is restriction. Take look at intake ports in head. They are much, much smaller than TB size. Where do you think major restriction exists?

It's like funnel with small [outlet]. You can increase diameter of inlet all you want. But flow-rate is limited by smallest section in path.

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Old August 20th, 2022, 10:54 PM   #138
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Quote:
Originally Posted by DannoXYZ View Post
Take look at intake ports in head. They are much, much smaller than TB size. Where do you think major restriction exists?

It's like funnel with small inlet. You can increase diameter of inlet all you want. But flow-rate is limited by smallest section in path.
You are correct. I'm all about measuring and calculating stuff. I googled a whole lot ITB sizes for different engines and ran the figures to get some idea. Namely about how much cross sectional area per cylinder hp the manufacturers have in ITBs. That got me thinking our bike's parts might be on the small side.
Edit, I did just that. Inlet port is under 28mm and narrows down from there.

Short video from yesterday, quickest lap is lap 14

Link to original page on YouTube.

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Old August 21st, 2022, 09:03 AM   #139
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The ergonomics have some what changed from stock
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Old August 21st, 2022, 09:48 PM   #140
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Yes, I prefer handlebars around seat-height. Chopped top of fairings off so I can lower bars 15cm.
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Old August 26th, 2022, 08:51 AM   #141
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When I repaired the front forks I set the oil level to exact factory specification. If I were to run more oil in them, how much is safe?
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Old August 28th, 2022, 02:06 AM   #142
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I have a long list of actually neccessary things I need to do on the bike. But, I'm planning on making the silencer bracket from titanium so save weight.
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Old August 28th, 2022, 09:16 AM   #143
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We measured the suspension sag . Front is OKish, rear too stiff. I lowered the rear one click, raised the front by 11mm to about stock height. My fork oil level question had to do with this. My thinking was, smaller airspace might raise the effective spring rate a bit. The rider said he'd be happier braking late and carrying a bit brake pressure in to corner entry if the front didn't pitch so much. Another zero budget idea I had was to add shims on top of the springs to raise the preload.
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Old August 28th, 2022, 10:51 AM   #144
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I believe you can add 3cm of extra oil to reduce air-volume. That seems to be amount Racetech suggested with their springs when I installed. Along with more preload should reduce diving under braking.
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