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Post by steve99 on Jul 8, 2025 10:51:31 GMT 1
Hi all,
I have just finished an RD350LC and it has no pull below 2500ish. Get it above and it flies
All carb setting are standard as are exhausts air filter etc
I have rebuilt quite a few of these LC’s now and never encountered this problem.
As it’s low range I have tried moving the air screw but makes no difference other than the tick over.
The bike will not set off unless you rev it up to around 3000
It had the mid range flat spot as well but after cleaning behind the brass balls that was sorted
carb setting currently
main jet 220
pilot jet 22.5
clip 3
needle 5k1
float height 21
air screw 1 1/2 turns out
all jets and emulsion tube all clear
Off load it ticks over and revs freely and smoothly
Bike totally standard apart from rebore to +0.75
Runs fine when cold on choke
Any ideas anyone?
cheers
Steve
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Post by arrow on Jul 8, 2025 12:29:07 GMT 1
No pull below 2500?
Can I ask, are you new to 2-strokes?
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Post by arrow on Jul 8, 2025 12:43:58 GMT 1
Back in the day, 2500 revs would move the bike, but would struggle with the extra weight of chips and curry under your denim jacket, if that makes sense?
2500 revs would prove to your Gran that bikes are safe things.
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Post by steve63 on Jul 8, 2025 13:09:59 GMT 1
To be fair he has said he's done a few of these so this one must be another level of flat and not just a newby expecting arm wrenching power from 2000rpm.
If the airscrew adjustment makes no difference then isn't that an indication that the drillings are blocked in that circuit?
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Post by steve99 on Jul 8, 2025 13:26:53 GMT 1
No pull below 2500? Can I ask, are you new to 2-strokes? I have been riding 2 strokes for 49 years so yes I do know 2 strokes I also have a RD125LC, RD250LC and a RD350F and they pull away cleanly I have been restoring bikes for years and the 350 is my 14th LC and never had this issue which is why I asked on this forum hoping someone else had any idea |
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Post by steve99 on Jul 8, 2025 13:28:36 GMT 1
To be fair he has said he's done a few of these so this one must be another level of flat and not just a newby expecting arm wrenching power from 2000rpm. If the airscrew adjustment makes no difference then isn't that an indication that the drillings are blocked in that circuit? Sounds like it possibly. Is that the other brass ball? thanks |
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Post by arrow on Jul 8, 2025 13:28:48 GMT 1
No pull below 2500? Can I ask, are you new to 2-strokes? I have been riding 2 strokes for 49 years so yes I do know 2 strokes I also have a RD125LC, RD250LC and a RD350F and they pull away cleanly I have been restoring bikes for years and the 350 is my 14th LC and never had this issue which is why I asked on this forum hoping someone else had any idea Ok, understood. So it's well below where it should be. I'm sure that can be put right. 👍 |
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Post by steve99 on Jul 8, 2025 13:33:31 GMT 1
I have been riding 2 strokes for 49 years so yes I do know 2 strokes I also have a RD125LC, RD250LC and a RD350F and they pull away cleanly I have been restoring bikes for years and the 350 is my 14th LC and never had this issue which is why I asked on this forum hoping someone else had any idea Ok, understood. So it's well below where it should be. I'm sure that can be put right. 👍 Yes it’s that flat if you slow down and let the revs drop there nothing until the throttle is opened quiet a bit and then the power comes back |
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Post by arrow on Jul 8, 2025 13:37:00 GMT 1
Is it any better if you wind the air screws almost right in? I'm thinking weak on the pilot circuit.
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Post by midlifecrisisrd on Jul 8, 2025 14:23:34 GMT 1
Are the carbs 4l0 00 or 01
Deffo sounds like a partially blocked pilot jet or an air leak
Steve
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Post by steve99 on Jul 8, 2025 15:26:01 GMT 1
4L0 01
Pilots are definitely clear. I going to take the carbs off again and also check the read valve gaskets aren’t leaking
As a last resort I suppose I could put my Rd250lc carbs on with the correct jets needle etc and try that as the 250 run really well
Cheers
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Post by steve63 on Jul 8, 2025 16:00:06 GMT 1
To be fair he has said he's done a few of these so this one must be another level of flat and not just a newby expecting arm wrenching power from 2000rpm. If the airscrew adjustment makes no difference then isn't that an indication that the drillings are blocked in that circuit? Sounds like it possibly. Is that the other brass ball? thanks I don't know, sorry. What I do know is that if the airscrews are further in it improves pick up from low revs. It also means you need to less choke before they respond properly to the throttle. The opposite is also true. I suppose that would only work if everything was clear. My lads YZ125 was really sluggish from a stand still and needed a good few revs and throttle to pull away cleanly. I noticed later that the airscrew was missing altogether. I robbed one from a KR1S carb and it was in there until the bike went years later. When I say went, it got nicked  . |
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Post by steve99 on Jul 8, 2025 16:50:49 GMT 1
Had the carbs and reeds out
Sprayed carb cleaner into the air screw holes and blanked the holes at the inlet. The spray came out of the same hole that pilot jet feed into. If they were blocked they are definitely not now.
Fitted new gaskets again as I had some spare
Will give it a run tomorrow and report back
Thank again for the ideas
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Post by steve99 on Jul 9, 2025 14:29:28 GMT 1
I’ve had the bike on the road and now it is as it should be. Strangely the air screw is only 1 turn out to get the best smooth pull away Not sure whether it was an air leak around the reeds or an air way blockage Thanks for the ideas Cheers Steve  IMG_1598 by Steve D, on Flickr |
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