Just bought a 2007 gs500f with 4000 miles. It wouldn't idle but I cleaned the carbs and now it idles nicely.
But, when I apply throttle slowly right as it gets to around 1800 rpm it makes a clunk sound and carries on to rev up normally. The bike also runs pretty lean.
I'm aware of the infamous camshaft endplay knocking sound but I thought that was only for pre 05 model years. I can try to get a video up tomorrow.
Thanks to anyone who can offer help.
Is this before the bike is warmed up fully?
After it was warm i think. Ill need to double check. It was a hot humid 95* day.
95F is a hot day, but it'll still take some running under load (about 15 mins) for the engine to reach operating temp. I get misfiring from a cold engine, which I believe is because the petrol doesn't vaporise as well and so you get a lean condition. If it's that, it should be better with the choke on until the engine is warmed up - I don't really get any misfiring at all until I take the choke off before the engine is warm (which I pretty much always do).
Otherwise, if I'm not mistaken, 1800 rpm (without load, so in neutral or clutch in) is right about when you're coming off the pilot jet in the carbs - someone here posted a graph showing when each jet comes into play, I'll see if I can find it.
Found it:
(http://justkdx.dirtrider.net/images/graph.jpg)
operating temperature of the MC is like 180F or higher. 95F is not even close.
There's such a variety of the term "knocking" and the regularity you are talking about, it's hard to know what to say.
While the later GSs had a spring washer that reduced the "clacking" noise which is about once every 2 seconds at idle from camshaft movement (which by the way is harmless), they all likely will make that noise eventually. So this could be it.
A "rod knock", or like a spun rod bearing or other low-end engine problem, which would be super unlikely at that mileage unless someone ran it out of oil, is strictly rhythmic with the engine speed and very much faster than that. At idle it'll make that noise on each compression stroke of the bad cylinder so if it idles at 1200 rpm then it'll knock 20x per second. If you had excessive valve clearance, a burnt valve, etc., then it'd make a more "tapping" kind of sound at 20x per second at idle. Both of these things will accelerate with engine rpm. Excessive valve clearance noise will likely reduce with higher rpms and a rod knock will get worse under load and higher revs.
There are a number of other things that can make a knocking type noise, but if it's like every 2 seconds I'd say 90% chance it's harmless camshaft side play, especially if it is noticeable only at/near idle.
Quote from: mr72 on July 02, 2018, 12:08:44 PM
operating temperature of the MC is like 180F or higher. 95F is not even close.
There's such a variety of the term "knocking" and the regularity you are talking about, it's hard to know what to say.
While the later GSs had a spring washer that reduced the "clacking" noise which is about once every 2 seconds at idle from camshaft movement (which by the way is harmless), they all likely will make that noise eventually. So this could be it.
A "rod knock", or like a spun rod bearing or other low-end engine problem, which would be super unlikely at that mileage unless someone ran it out of oil, is strictly rhythmic with the engine speed and very much faster than that. At idle it'll make that noise on each compression stroke of the bad cylinder so if it idles at 1200 rpm then it'll knock 20x per second. If you had excessive valve clearance, a burnt valve, etc., then it'd make a more "tapping" kind of sound at 20x per second at idle. Both of these things will accelerate with engine rpm. Excessive valve clearance noise will likely reduce with higher rpms and a rod knock will get worse under load and higher revs.
There are a number of other things that can make a knocking type noise, but if it's like every 2 seconds I'd say 90% chance it's harmless camshaft side play, especially if it is noticeable only at/near idle.
I interpreted it as a misfire - the post read to me like it makes a clunk and briefly pauses revving, and then carries on revving up. Is that right? I experience that myself if I hold the bike at that RPM when cold so would be interested to see if it was actually a problem.
yes kookas is pretty spot on with how the engine behavior is. we havent ran it for more than 10 minutes with fear that we were damaging the rods or something. so not entirely sure if it was 100% warmed up.
it could be the jets switching over. when we rebuilt the carb the screws that come off the main jet and the smaller pilot jets look identical accept for a larger hole. we put the large hole ones on the main jets and the small hole ones into their housing. is this correct?
in addition we just checked the cams and cam chain to see if there was any looseness or play. the cam chain deflected about 4mm and the cams dont budge. not sure if shimming the valves would help but we did not do that.
so based on these symptoms would you guys say it's safe to run for long periods of time and maybe even ride?
thanks.
Sounds like you are describing a stumble or hesitation.
The title says "engine knock every 2-4 seconds" which is completely different to me. So my comments were about a knock, not hesitation.
Your other issue is likely a vacuum leak or some other problem in the carbs, which is not serious and will not prevent you from riding. Any serious issues will manifest once you can get it fully warmed up. You can do a valve clearance check but even if it has tight valves it won't prevent you from using the bike, it'll just maybe make it hard for it to idle when it's fully warmed up, which you will definitely notice.
I warmed the bike up for awhile and the stumbling improved but was still there. I then took it for a short ride and it ran fine but was running very lean.
anyone know about the jet sized I mentioned earlier?