I broke something (i think) and I dont know what it is.

[GfromLT]

Hello, 

Im new rider and Ive just recently bought 98' yamaha xj600s diversion. Motorcycle was okay-ish condition, but Ive done something incredibly newbish and stupid.

So what happend you ask? I was gooning down the road at 120kmh (70 mph, roughly), a stack of cars far head was visible, so I started braking, but didnt notice my braking wasnt doing much and I lost sence of speed, so at roughly that speed I shifted into 3rd gear (couldve been 2nd gear, cant tell anymore) dumping the clutch, bike made strange sounds, engine stalled and I rolled to a stop. When stopped I couldnt start the bike, for sure I thought it was done. I pushed it back to the garage and left it be. After few hours and pulling the choke all the way, bike started, but now I THINK it is making a ratling/knocking sound at low rpm that wasnt there before.

 

Got some videos:
Just after buying the bike, before screwing it up:

 

 

How it is now starting without choke when WARM:

 

 

I really dont like the sounds its making when rpm is ~1k.

 

Here how its working COLD-ish:

 

 

 

I check all 4 exhaust headers they were hot, so the cyllinders are firing. Plugs are not lose, I didnt remove them tho.

From common knowledge, to me the knocking sound at ~1k rpm sound like camshaft, crackshaft or pistons or something in between vibrating the way they shouldnt.

Tell me straight doc, how bad is it?

Edited April 19, 2022 by GfromLT

[Mississippi Bullfrog]

At low tickover they can sound like a bag of spanners. It is actually quite hard to break a bike engine just by revving it unless you seriously go into the red zone. They aren't as fragile as people often think. How fast were you going when you dumped the clutch? 

 

Invest in a mechanic's stethoscope, they are cheap and the best way to check the source of odd noises. In the meantime a big screwdriver does the same. Stick the tip to the engine, put your ear to the handle, keep hair and clothes away from moving parts.

 

You can easily track down internal noises this way.

Edited April 19, 2022 by Mississippi Bullfrog
Typo...are / aren't

[GfromLT]

8 minutes ago, Mississippi Bullfrog said:

They are as fragile as people often think.

I assume you mean "They arent..."

 

Thats a great advice with the screwdriver, I will try that. It is driving me nuts, could be simple clutch rattle, could be engine bearing failure 

[Mississippi Bullfrog]

Sorry, yes, I meant aren't. It's my crappy phone.

 

If you're worried drop the oil. If something broke there will be bits of debris in the oil. 

[GfromLT]

I could do that, just today I bought 4L of motul 5100 and oil filter, however the bike is starting and it runs (with allmost full choke) and gears seems to be fine, so I doubt there would be any pieces, but cant know for sure until drained.

[Bianco2564]

Things that spring to mind for over revving an engine.

Valves could have clipped the pistons and bent the valves.

Can you do a compression check or leakdowns? Check the valve lash, shim could have jumped off.

Cam timing could have jumped or stretched the chain, check the marks line up while you are checking the valve lash.

Damaged the chain tensioner.

Broken valve spring.

Damaged retainer or collets.

 

[fifthwheel]

I can hear one cylinder has low compression on cranking the engine.

Edited April 20, 2022 by fifthwheel
spelling

[GfromLT]

I played around with the bike today trying different scenarios. What I noticed was:
- When cold bike starts up okay-ish with choke half-way pulled. Giving throttle makes engine go VROOOOM.
- putting it in gear, without releasing the clutch, makes RPM go down 1.5-2k (wtf?)
- Idle rpm isnt stable (when fired up with choke, 3k rpm, going up and down +-300rpm.
- I left it to idle for as long as it could. While engine is hot, it doesnt wannt to start even with choke, If it does start, rpm rises to ~4k because of how much choke is pulled and then start falling, falling, and stalls in like 2 minutes of total idling
-While RPM is falling, twisting throttle kills the engine.
https://www.youtube.com/watch?v=fpa-yIf46hg

Tried to push bike in different gears, there is some free play, but gears are there. Engine knockin indeed is clutch rattle. Didnt find anything metal in engine oil.

At this point it has to be the fueling?

[Mississippi Bullfrog]

I would check the clutch adjustment. Sounds like it's dragging. If the rpm drops when you engage a gear but are holding the clutch lever then that sounds like the clutch is partially engaged.

 

Fuelling may be off if it isn't starting from hot but you shouldn't use choke for a hot start anyway. A hot engine has greater compression than a cold one so problem with hot starts can also be battery or starter related.

 

The YouTube clip could also be an ignition issue or an air leak. Don't try to change too many things at once. You just end up in a muddle. 

 

Start with the basics, check the plugs for a good spark, check the air filter is clean. Check the timing is right. 

 

 

[Fozzie]

On 20/04/2022 at 17:44, GfromLT said:

I played around with the bike today trying different scenarios. What I noticed was:
- When cold bike starts up okay-ish with choke half-way pulled. Giving throttle makes engine go VROOOOM.
- putting it in gear, without releasing the clutch, makes RPM go down 1.5-2k (wtf?)
- Idle rpm isnt stable (when fired up with choke, 3k rpm, going up and down +-300rpm.
- I left it to idle for as long as it could. While engine is hot, it doesnt wannt to start even with choke, If it does start, rpm rises to ~4k because of how much choke is pulled and then start falling, falling, and stalls in like 2 minutes of total idling
-While RPM is falling, twisting throttle kills the engine.
https://www.youtube.com/watch?v=fpa-yIf46hg

Tried to push bike in different gears, there is some free play, but gears are there. Engine knockin indeed is clutch rattle. Didnt find anything metal in engine oil.

At this point it has to be the fueling?

 

In one of your videos, it just sounds a cold old bike idling too low. My Blackbird makes an industrial "chugga chugga clunk" noise when it's idling too slow when I start it. The clutch basket is known to be a bad fit, and it's probably that not spinning quickly enough. Goes nice and smooth when revving over 1100rpm though. 

 

Can you ride the bike, get the engine warm, and let us hear it idling again? 

 

RPM falling when you clutch in and select a gear is just clutch drag. Lots of bikes do it, even if the clutch is well adjusted. Get the back wheel off the ground with a paddock stand, run it, pop it in gear with the clutch in and watch how much the back wheel spins.