Engine noise under load when hot

[Targan]

Hey guys,
My bike has the big bore kit, advanced ignition timer and it's tuned rich to keep it cooler. When my bike gets really hot and I take off from a stop it makes a loud clacking noise that follows the speed of the rpms and stops after about 3k rpm. In second gear if I accelerate super hard (only when hot) it does the same until about 6k rpm. Was curious if this is an overheating issue, common problem, or damaged something? I have done nothing to the bike recently, it's just been getting hotter outside.
Thanks for any info

[ribbert]

Hey guys,
My bike has the big bore kit, advanced ignition timer and it's tuned rich to keep it cooler. When my bike gets really hot and I take off from a stop it makes a loud clacking noise that follows the speed of the rpms and stops after about 3k rpm. In second gear if I accelerate super hard (only when hot) it does the same until about 6k rpm. Was curious if this is an overheating issue, common problem, or damaged something? I have done nothing to the bike recently, it's just been getting hotter outside.
Thanks for any info

"Clack" is not normally a word used to describe engine noises. It may well just be a difference in the local vernacular, but if it is a "clack" have you checked your chain and sprockets recently?

Noel

[andyb]

Plug check as well, preferably by using the killswitch and coasting with the engine not moving after it's done it for a spell.

[FJ_Hooligan]

Sounds like detonation to me (spark knock).
If it's hot and under load (with a lot of compression and advance) then you could be doing bad things to the motor!
Can you roll off the throttle (thus reducing the load) and make it stop?

[andyb]

That's my thought too.  Plugs should show it clearly if it's that bad.

The other easy thing to try would be a tank of 100 octane (or higher, whatever's available... if you're rich and it's warm out, you should be okay even with an oxygenated fuel).  It'll make the performance go a bit soggy, but should fix a preignition issue.

[FJ_Hooligan]

That's my thought too.  Plugs should show it clearly if it's that bad.

If it's detonation there will be flakes of aluminum on the plugs.  The source of the aluminum would be the tops of the pistons spalling off.  Not to mention what the explosive hammering is doing to the rod and main bearings.

[Targan]

Oh no! This is what I feared. I am not the mechanically savvy type so forgive me for my errors. Hopefully I have not destroyed my engine (seems fine now). This has only happened a few times, but those few times it was doing it quite a bit. I'm going to bring it to my friend for a diagnostics check. If it were my chain and sprockets (which I do need to replace) why would only do it if it's hot? (curious)

[ribbert]

What about your oil level? If it is too low the oil will surge under acceleration leaving the pump pick-up sucking air and run out of oil pressure which will make the motor sound "clacky" and return to normal when you stop accelerating. Oil thins as it gets hot and is more prone to sloshing around.

I can't see why being bored, running a few degrees advance and a bit rich would have any bearing it.

Start with the simple stuff, it won't take long to check and eliminate the chain and sprockets and oil level.

Noel

[Targan]

What about your oil level? If it is too low the oil will surge under acceleration leaving the pump pick-up sucking air and run out of oil pressure which will make the motor sound "clacky" and return to normal when you stop accelerating. Oil thins as it gets hot and is more prone to sloshing around.

I can't see why being bored, running a few degrees advance and a bit rich would have any bearing it.

Start with the simple stuff, it won't take long to check and eliminate the chain and sprockets and oil level.

Noel

OH MY GOD I have got to be the stupidest person here. I forgot I swapped oil coolers. I didn't install it tight enough so oil spurtted out everywhere and I forgot to fill it back up to recommended level when I fixed it. The oil light never came on so I never thought about it. Just checked and it was low. I'll have to see if my bike ever repeats this issue in the future! Chain is clean and tightened, but does have a tight spot. Will be replacing that soon. Scheduled to bring my bike in for a diagnostics next week too. It just hit it's 50,000th mile so it deserves some "spa time" haha.
Thanks for the help guys!

[Targan]

Update: Got my bike SUPER hot again, the noise still happens, but just barely and only when I'm pinning the throttle! So problem solved I guess lol. It doesn't do it anymore with normal riding. Also as far as highway miles go my bike stays nice and cool (relatively) and doesn't overheat even in 110+ degree weather all thanks to Randy's oil cooler! My bike was an absolute trooper on an 80 mile ride the other day. 

[ribbert]

Update: Got my bike SUPER hot again, the noise still happens, but just barely and only when I'm pinning the throttle!

It is possible to get these engines so hot they will make strange noises that are unrelated to anything other than being too damn hot, what I would call SUPER hot. As far as your noise goes, there may be some residual damage from running it low on oil that becomes apparent when SUPER hot.
These engines are reasonably forgiving, just try not to let it get that hot. If you are stuck in barely moving traffic in 100 deg+ temps for long periods of time on a regular basis, find some other mode of transport.

Unlike a lot of older air cooled 4's, these things are not bullet proof when it comes to heat, you can seriously overheat them.

Noel

[Pat Conlon]

Hey guys,
My bike has the big bore kit, advanced ignition timer and it's tuned rich to keep it cooler. When my bike gets really hot and I take off from a stop it makes a loud clacking noise that follows the speed of the rpms and stops after about 3k rpm. In second gear if I accelerate super hard (only when hot) it does the same until about 6k rpm. Was curious if this is an overheating issue, common problem, or damaged something? I have done nothing to the bike recently, it's just been getting hotter outside.
Thanks for any info

When you say "tuned rich" what exactly do you mean?  What size are your pilot and main jets?
In the desert, with a high compression 1314 engine, it is entirely possible that you need 42.5 pilot jets...
I know this to be true, because I need them with my 1350 engine...I tried #40's but no go.....our toasty desert is unique.

[Targan]

Hey guys,
My bike has the big bore kit, advanced ignition timer and it's tuned rich to keep it cooler. When my bike gets really hot and I take off from a stop it makes a loud clacking noise that follows the speed of the rpms and stops after about 3k rpm. In second gear if I accelerate super hard (only when hot) it does the same until about 6k rpm. Was curious if this is an overheating issue, common problem, or damaged something? I have done nothing to the bike recently, it's just been getting hotter outside.
Thanks for any info

When you say "tuned rich" what exactly do you mean?  What size are your pilot and main jets?
In the desert, with a high compression 1314 engine, it is entirely possible that you need 42.5 pilot jets...
I know this to be true, because I need them with my 1350 engine...I tried #40's but no go.....our toasty desert is unique.

Honestly I don't know the size, just that the previous owner had it done. It has an aftermarket fuel/air ratio gauge on the dash and it's 3/4's of the way to the top which is slighty rich.

[Pat Conlon]

Time for you to get dirty. Pull your carbs, take the jets out and tell us what your running.

No more guessing.

[ribbert]

Time for you to get dirty. Pull your carbs, take the jets out and tell us what your running.

No more guessing.

Pat, this development unfolded while you were at the rally, the source of the problem appears to have been found.

What about your oil level? If it is too low the oil will surge under acceleration leaving the pump pick-up sucking air and run out of oil pressure which will make the motor sound "clacky" and return to normal when you stop accelerating. Oil thins as it gets hot and is more prone to sloshing around.

I can't see why being bored, running a few degrees advance and a bit rich would have any bearing it.

Start with the simple stuff, it won't take long to check and eliminate the chain and sprockets and oil level.

Noel

OH MY GOD I have got to be the stupidest person here. I forgot I swapped oil coolers. I didn't install it tight enough so oil spurtted out everywhere and I forgot to fill it back up to recommended level when I fixed it. The oil light never came on so I never thought about it. Just checked and it was low. I'll have to see if my bike ever repeats this issue in the future! Chain is clean and tightened, but does have a tight spot. Will be replacing that soon. Scheduled to bring my bike in for a diagnostics next week too. It just hit it's 50,000th mile so it deserves some "spa time" haha.
Thanks for the help guys!

Update: Got my bike SUPER hot again, the noise still happens, but just barely and only when I'm pinning the throttle! So problem solved I guess lol. It doesn't do it anymore with normal riding.

Noel