10-20-2023, 10:26 AM | #1 |
Join Date: Feb 2021
Posts: 994
|
KPX Down Shift clunk ???
I have been racking up the miles on the KPX, and now have well over 200 on the odometer. I went to Point Pleasant, and Gallopolis yesterday, and Gallopolis in particular had a lot of traffic lights on it's main drag along the river. I have noticed is since I got the bike, but if you know that you're going to be stopping, and pull in the clutch, and just coasting, braking ,and down shifting while keeping the clutch pulled, the shift into first is a harsh like clunk, unless you are nearly stopped. I'm not talking about fast speed, I'm talking about just normal common sense, just like I have always ridden my TBR7, Hawk, and Brozz that I have had. There is no over travel below first on the KPX, but other than that,the bike shifts just like the other bikes. My idle is always around 1500, clutch properly adjusted, and neutral is easy to find. I have started treating 1st in the bike as a gear that I don't shift into till I am almost stopped, and I can deal with that, but I also am curious if it's normal for the KPX. If my bike has issues,I would like to have them took care of while under warranty. Thanks
|
|
10-20-2023, 10:31 AM | #2 |
Moderator
Join Date: Oct 2016
Location: Houma, La.
Posts: 11,707
|
I get a slight clunk but all my bikes do that. Even my Vulcan S. It's less when I adjusted the clutch lever with minimal play. It also does it less with synthetic oil.
__________________
2024 Linhai 300 ATV 4x4 2023 Lifan Lycan 250 Chopper 2023 Venom Evader 2022 Lifan KPX250 2020 Kawasaki Vulcan S (Sold) 2004 Honda ST 1300 2016 Black Hawk 250 (sold) Keihin PE30 carb,125 main,38 slow.Pod filter,ported & decked head 10:1 CR,Direct Ignition Coil,15/40Sprockets,NGK DPR8EIX-9,De-Cat,Dual Oil Cooler,Digital Cluster 2016 Cazador180 XL 2014 Coolster150 JerryHawk250.com My YouTube Channel |
|
10-20-2023, 10:53 AM | #3 |
Join Date: Feb 2021
Posts: 994
|
Maybe I notice it more on this bike because it's quite, and first is pretty low. It may improve after break in, and I switch to synthetic. My clutch is adjusted with minimal play. I was also wanting to ask if you can recommend a feeler gauge well suited to adjusting the valves? I took my tank fairing off yesterday, before firing the bike up, I intended to only check the exhaust valve clearance, because I didn't want to strip all the plastic, tank, seat, and rack off the bike yet. I took the little cover off, and was surprised at how difficult it seems to get a feeler gauge in there. I took the 0.10 mm blade off my set, and tried to bend the end to get enough angle on it to go in the opening, and between the valve stem, and set screw. It was just thick enough that it cracked , and I couldn't chance loosing it in the hole, so I didn't adjust the exhaust valve. I did verify that I have some play, so I just put everything back together. I plan on sending the ECU to Lifan after the upcoming warmer weather that we are supposed to get next week, and I want to do a though valve adjustment then.
|
|
10-20-2023, 11:45 AM | #4 | |
Moderator
Join Date: Oct 2016
Location: Houma, La.
Posts: 11,707
|
Quote:
__________________
2024 Linhai 300 ATV 4x4 2023 Lifan Lycan 250 Chopper 2023 Venom Evader 2022 Lifan KPX250 2020 Kawasaki Vulcan S (Sold) 2004 Honda ST 1300 2016 Black Hawk 250 (sold) Keihin PE30 carb,125 main,38 slow.Pod filter,ported & decked head 10:1 CR,Direct Ignition Coil,15/40Sprockets,NGK DPR8EIX-9,De-Cat,Dual Oil Cooler,Digital Cluster 2016 Cazador180 XL 2014 Coolster150 JerryHawk250.com My YouTube Channel |
|
|
10-20-2023, 12:17 PM | #5 |
Join Date: Feb 2021
Location: Kansas City
Posts: 2,625
|
The transmission should be tight on a new motorycle. It will get looser and not clunk as loudly over time. But no reason to shock the engine with early downshifts while it is still breaking in. Just wait until you are going real slow for now or try to match engine approximate rpm to the gear you want when you shift to that gear (at idle). The dogs won't shock the transmission so much when they slide in.
__________________
-NOS 2020 KTM 250SX (2-stroke motocross) |
|
10-20-2023, 12:50 PM | #6 | |
Join Date: Feb 2021
Posts: 994
|
Quote:
|
|
|
10-20-2023, 02:13 PM | #7 |
Join Date: Feb 2021
Location: Kansas City
Posts: 2,625
|
During downshift coming to a stop, even with the clutch pulled, if the part of the transmission connected to the spinning crankshaft which is idling (the input shaftcounter shaft-counterspinning shaft, or main shaft in the transmission) is spinning much slower than the forward spinning side (connected to the rear sprocket/wheel), the dogs on the side of the gear has to abruptly change the speed of the input shaft to go into the next gear as you downshift. This is the situation when the engine is idling, and the motorcycle is rolling to a stop. This shocks the transmission bearings, seals, dogs, and even the contact between the gears and the shafts. The input shaft spins even with the clutch pulled, and it is spinning slowly at idle.
It is not possible to precisely match the rpm of the engine to exactly the speed of the output shaft for a given gear every time, but the farther away it is, the more shock the transmission experiences. OK, you say it is worst going down to first, but that is the lowest gear so it makes some sense. Ever seen someone rev the engine, pull the clutch, then slam it into first without waiting for it to return to idle. Yeah. LOUD crack. This is because even with the clutch pulled, the main shaft (counter spinning shaft) is spinning FAST since the clutch has some friction even with the clutch pulled, turning the main shaft/counter shaft, and the output shaft is NOT TURNING at all since it is connected to the rear sprocket and the wheel is not turning. Putting it in gear instantly stops the input shaft (breaks the clutch loose). That is a major shock to the transmission. Downshifting at speed with the clutch pulled is the same thing, but with reversed forces. You have to shift! I know But try to wait until the difference in the countershaft and output shaft (for the gear you will shift into) is as close as possible. It WILL get better as the transmission is broken in, or worse if the transmission is subjected to repetitive shock. The quieter the shift, the closer you came to matching the speed of these two shafts, for a given transition. I usually put the engine in first gear, pull the clutch and break loose the clutch (rolling forward/back) BEFORE I start the bike (after warm up). Yes, I will actually turn it off after warm up and do this. So my transmission experiences NO shock at all when I do that. It is much gentler on the entire transmission. When you pull the clutch, the input shaft (main shaft/coutershaft) keeps spinning! Putting it in gear stops it from spinning, abruptly!
__________________
-NOS 2020 KTM 250SX (2-stroke motocross) Last edited by Thumper; 10-21-2023 at 08:22 AM. |
|
10-20-2023, 03:28 PM | #8 |
Join Date: Aug 2022
Posts: 175
|
I'm over 9250 miles on my KPX and I've experienced the "clunk" up until just a week ago when I did my 9th valve adjustment and replaced the spark plug. My exhaust valve was a little tight and I think I did the best adjustment I've ever done on the valves (intake did not need any adjustment) and the bike now seems to be running and shifting better than it ever has. I can even tell a difference in how it sounds. I changed the plug because it was getting pretty gray but thing adjusting the exhaust valve spot on is what really made the difference. I'm not getting quite the clunk and it seems to be shifting better over all. I've been using Rotella T4 for most of the miles and thought about changing to synthetic but didn't think that would make much difference since I've been changing the oil and filter between 1200 and 1500 miles. I have plans to do a 200 mile loop through the mountains tomorrow and have a goal to hit 10,000 miles by next month.
__________________
2022 Lifan KPX 250 |
|
10-20-2023, 09:56 PM | #9 |
Join Date: May 2018
Posts: 1,639
|
You are not downshifting properly if you are actually doing it like you claim in post #6 above ,you are going to hurt yourself and your bike if you continue slowing down while riding the brakes with the clutch pulled .I would imagine there is probably a basic motorcycle riders instruction somewhere on the net ,but any manual transmission instruction for cars and trucks would be just as good to learn basic clutch and shifting skills .
|
|
10-20-2023, 10:44 PM | #10 | |
Join Date: Feb 2021
Posts: 994
|
Quote:
Last edited by Bill Hilly; 10-20-2023 at 11:43 PM. |
|
|
10-21-2023, 05:32 AM | #11 |
Join Date: Feb 2021
Location: Kansas City
Posts: 2,625
|
When I begin slowing down, I do periodically pull the clutch and blip the throttle, down shift and drop the clutch to engine brake. But I try to match RPM so the it is minimally shocking. But I only do this maybe once or not at all. I let it engine brake, then when I reach idle in gear, I pull the clutch and gently downshift at idle while still rolling. One by one, back to first. Sometimes only to second if traffic is still crawling. Engine braking is fine. It is the shifting that needs to be smooth!
It sounds like you are doing something like this, downshifting at low speed. Engine braking is no problem, but wait until you are near idle before pulling the clutch and gently downshift while still rolling. You should be able to get into first without shock sometimes, when RPM matches input/output in the transmission. I often allow it to pause in neutral at idle, low rolling speed on my way to first. It can help avoid the thunk.
__________________
-NOS 2020 KTM 250SX (2-stroke motocross) Last edited by Thumper; 10-21-2023 at 09:10 AM. |
|
10-21-2023, 09:21 AM | #12 | |
Join Date: Feb 2021
Posts: 994
|
Quote:
|
|
|
10-21-2023, 10:39 AM | #13 |
Join Date: May 2018
Posts: 1,639
|
What was written above was that you were pulling in the clutch lever ,and holding it while riding the brakes to a stop .At least that is what I was reading .Now you are saying you are using the engine braking to slow you down ,but I certainly didn’t read anything about that in post #6 ,above .
|
|
10-21-2023, 11:00 AM | #14 | |
Join Date: Feb 2021
Posts: 994
|
Quote:
|
|
|
|
|
|
|