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Post by jollyr6 on Aug 22, 2017 8:42:22 GMT 1
Hi all I know this has been covered before
I've done a full rebuild on engine and I'm running it in but she seems sluggish low end I'm only taking her to 4K for at least 50 miles is she sluggish because of gianelli pipe anyone got any suggestions is it carb related jets etc cheers for now jolly
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Post by wonkywheel on Aug 22, 2017 20:02:36 GMT 1
Hi, It could be a combination of both- don't expect too much at low revs, especially as we are a tad more bulky these days.  When i ran my little LC single in, once i got to about 50 miles, i started to increase the revs. I'm sure you are aware- just don't ring its neck, and don't labour the engine. I prefer a standard air filter set up. Get the miles in; keep checking ya plug- it takes a while to get a good set up, and that's all the fun of our madness. |
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Post by mattybeckett on Aug 22, 2017 22:09:28 GMT 1
Early days/miles yet.. still might be a bit tight. id do another 50 miles before looking for problems and get the hot/cold cycles in, at least 5 times. Five ten mile trips would be my choice and let engine get hot and cold each time.
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Post by visakhrd on Sept 11, 2017 7:06:01 GMT 1
Hi, It could be a combination of both- don't expect too much at low revs, especially as we are a tad more bulky these days. When i ran my little LC single in, once i got to about 50 miles, i started to increase the revs. I'm sure you are aware- just don't ring its neck, and don't labour the engine. I prefer a standard air filter set up. Get the miles in; keep checking ya plug- it takes a while to get a good set up, and that's all the fun of our madness. I have never rode an 125LC before until recently. It was not available in this part of the world . I dont have another vehicle in another 2000 miles to compare as well. The bikes I have are RX135 and RD350 which are very responsive at all RPM's Does all LC's run sluggish in lower RPM's. Is it because of the chamber(Exhaust). what does ring its neck means? |
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Post by Yogi on Sept 11, 2017 7:26:52 GMT 1
Ring it's neck means scream it in every gear to keep the revs high
Most two strokes can seem sluggish if the revs are low
Ride them like you stole them
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Post by looey on Sept 11, 2017 18:47:44 GMT 1
If it's a Non-YPVS engine and has a non-standard pipe, it will have pretty much no power at all under 5.5/6k I'd say my Mk1 won't even pull through the mid-range in any gear other than 1st & 2nd gears. But,...... get it over 6K and it's like a motorcross bike through the gears   |
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Post by visakhrd on Sept 15, 2017 5:26:38 GMT 1
Ring it's neck means scream it in every gear to keep the revs high Most two strokes can seem sluggish if the revs are low Ride them like you stole them Thank you Yogi. my bike basically crawls in low RPM's. Partly reason might be because I'm using a RD250LC 4L1 carb in it. but in higher RPM's the bike goes like a rocket. |
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Post by museumman on Sept 21, 2017 11:07:44 GMT 1
Ring it's neck means scream it in every gear to keep the revs high Most two strokes can seem sluggish if the revs are low Ride them like you stole them Thank you Yogi. my bike basically crawls in low RPM's. Partly reason might be because I'm using a RD250LC 4L1 carb in it. but in higher RPM's the bike goes like a rocket. Depends what you mean by sluggish/crawls, that would suggest a fault to me and it's not pulling properly. But a standard bike should still respond well to the throttle at lower revs and will pull other gears but it wont be making the power it is tuned for, it is a 2-stroke after all. You should be able to just cruise a long with no drama until you push it into the power band then it becomes a different character at 5500RPM to 9000RPM. For more low down torque you would narrow the exhaust but then lose out at the top end, which is why the YPVS was invented for the best of both worlds. Even then, people will still try and adjust the curve to suit them for the roads/track they are riding on. The standard bikes are designed to be as useable as possible on public roads with an acceptable life expectancy. Compare them to a racing Kart motor that really doesn't have anything under 9,000 RPM (new motors are run-in in at 11,000RPM then revved to 17,000RPM after 10-15 min running in session then rebuild again after 5-6 hours, and that was considered a long-life eco formula, the top karts went to 20,000RPM) I put my bikes back to standard with maybe improved ignition components as 2-stroke tuning becomes a minefield and not worth the time unless you're competing on a circuit or have really exciting local roads. |
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Post by visakhrd on Sept 26, 2017 7:15:48 GMT 1
Thank you Yogi. my bike basically crawls in low RPM's. Partly reason might be because I'm using a RD250LC 4L1 carb in it. but in higher RPM's the bike goes like a rocket. Depends what you mean by sluggish/crawls, that would suggest a fault to me and it's not pulling properly. But a standard bike should still respond well to the throttle at lower revs and will pull other gears but it wont be making the power it is tuned for, it is a 2-stroke after all. You should be able to just cruise a long with no drama until you push it into the power band then it becomes a different character at 5500RPM to 9000RPM. For more low down torque you would narrow the exhaust but then lose out at the top end, which is why the YPVS was invented for the best of both worlds. Even then, people will still try and adjust the curve to suit them for the roads/track they are riding on. The standard bikes are designed to be as useable as possible on public roads with an acceptable life expectancy. Compare them to a racing Kart motor that really doesn't have anything under 9,000 RPM (new motors are run-in in at 11,000RPM then revved to 17,000RPM after 10-15 min running in session then rebuild again after 5-6 hours, and that was considered a long-life eco formula, the top karts went to 20,000RPM) I put my bikes back to standard with maybe improved ignition components as 2-stroke tuning becomes a minefield and not worth the time unless you're competing on a circuit or have really exciting local roads. Thank you , I have ordered a 10W carb off ebay, I shall post updates once the carb has been changed. |
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Post by yamyzee on Dec 28, 2017 12:30:18 GMT 1
Running in periods differ greatly due to piston clearences.....high perfoance 2 strokes run bigger clearances than road engines and require less running in.for example when my bro bought a new yz many,many years ago the yamaha manual said to pre mix some fuel at 25-1
start the bike and let it idle,revving occaisionly until hot.stop it,let it go stone cold then repeat the idleing/hot-cold process until the fuel was gone.then premix some more at 40-1 and thrash the sh#t out of it as you would any motocrosser.i asked my dad (a top engineer) why the hot/cold low rev process to which he replied "to let the soft rings work harden and take the shape of the bore".current school of thought is 'agressive running in' and to thrash it mercilessly from cold from new.............my opinion is a fairly low tuned engine like a 125lc has much tighter tolerances for longevity and fairly low power and requires a few miles of 'bedding in'.the crap out of powerband power is prob down to poor carb jetting,crap exhaust design or a combo of the 2......
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