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Discussion Working up

Discussion in 'Yamaha 250cc In-Line 4's' started by driftwood, Mar 15, 2022.

  1. driftwood

    driftwood Active Member

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    EXUPectomy.
    This 3LN5 is gutless below 9thou, which is where I ride my 3LN3 anyway. Unsure about topend, until I dyno it - so before testing I'm up for suggestions. It sure as hell roars past 10k.
    Had to go open pipe, but it's for-real - 12cm longer than std to allow for the Z-bend inside a std. Sanded down the air-filter element to get more, and cut wider airbox inlet.
    Engine/water temp is normal, but perplexed that headers are some 200deg less than previous after a mountain blast (cooked #2 much earlier, ignore colour)

    IMG_20220314_142409_866.jpg
     
  2. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    No EXUP will do that, it actually makes a difference on these.

    If you have a standard set of headers with the EXUP and cables, chuck them on and compare.
     
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  3. driftwood

    driftwood Active Member

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    Yeah but... tinkering. Yes, loved the pull from 7thou with std pipes - however wondering what topend can deliver. Clutch copes well with a handful of revs and slip to get away.
     
  4. driftwood

    driftwood Active Member

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    Plus, it may just nurse my license until lost points expire. Speed requires a conscious decision (all demerits came from the R1150, where a second can cost dearly)
     
  5. driftwood

    driftwood Active Member

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    Oops, 3LN6 (LN5 was typo/brain fart). Reverted to EXUP, due to economy <30%. Disappointed by track day topend so refitted headers and popped in 3LN3 CDI. Woohoo .... sandy coloured plugs. Seems faster than the LN3 (will have to borrow a rider to race the two against each other).
    Does anyone know what timing is on LN6?
    3LN3 specs say 46deg advance at 6000
     
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  6. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    3LN6/7 were down on power 40HP, looks likely that some of that power loss comes from the TCI
     
  7. driftwood

    driftwood Active Member

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    This final retry was time-kill during my painting of the std exhaust. If the Yam eng dept really knew what they were doing they wouldn't have used such crap steel.
    Anyhoo, it's a goer. Bush dyno of a long climb where prev couldn't hold 100kph, and it's now accelerating all the way. I'll revert to EXUP to double check that headers, and not just the TCI swapover, have benefitted (once rain clears)
     
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  8. driftwood

    driftwood Active Member

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    With 3LN3 TCI and its Zeal(?) cams this LN6 becomes really pleasant. Often found that I'm pulling 6th thru the burbs and, despite going up the Mts to test topend, consumption dropped ~20%
    But with headers on again, this is just a nasty machine. Even with std muffler it snarls... maybe some placebo effect going on but, if ridden like an LN3 ie revs>8k always, I reckon it's a contender.
     
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  9. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    The 3LN6/7 and Zeal cams/TCI come with reduced redline, but a slight increase in torque. The Zeal also runs 4-2-1 system with no EXUP and smaller carbs / inlet manifolds. 3LN6/7 and Zeal have improved emulsion needle retension and vacuum slide/springs with better needle retention are a nice fit into the 3LN3/5 carbs (Zeal slides might be slightly smaller and may not work)

    I had a 3LN6/7 donk with 3LN1 TCI and it wasn't really happy revving to 18,500rpm instead of 16,500rpm, valvetrain got a bit chattery, same as when I accidentally over-revved my ZXR at wakefield.

    Modified air filter might cause iffy fueling when combined with headers/exhaust and no EXUP. Personally I would keep the EXUP no matter what's required. The standard exhaust cans are heavy and contain all the baffles/emissions stuff etc, improvements to be had with aftermarket exhaust can are mostly noise and weight reduction, it may well flow better but dyno testing would be needed along with jetting changes. It's a long road to go down.

    Properly tuning the pilot mixture screws, and carb balance will make a huge difference. My 3LN3 went really well after, I think I got nearly 300KM out of a tank sitting at 110km/h coming back to Sydney from Tamworth once.
     
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    Last edited: Sep 28, 2022 at 9:24 PM
  10. driftwood

    driftwood Active Member

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    I've two sets of LN6 carbs (Litetek'd) on my LN3 and LN6. Sure, there's some mixture tinkering to go smoother thru the 8000 kick-in-the-bum with headers. But with an LN3 for social riding, and a mean LN6 for days when you want to surprise the bejesus out of others I've covered my options. EXUPworldwide has ideas on RAMair for FZR1000, which are inapplicable to the 250.
     
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  11. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    FZR250 has the air tubes and holes in the frame for "RAM air" but they stop there - not connected to airbox. If you want a similar RAM air system have a look at the 98-02 YZF-R6 bits. Small air inlet on the nose cone, large diameter rubber 'hoses' through the frame directly to airbox before the filter.
     
  12. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    and they will start to work at about 125mph :)
     
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