Rod knock?

[Himer]

Hi,

Today was very hot day of autumn in my country and I went for a ride. When I was close to the garage, engine started making very weird noises. I was aware that my clutch basket is knocking badly but that sound even supressed clutch basket it bangs so bad. When stationary it happens around 2500-3000 rpm, while riding it's just...

I have used stethoscope if I am not wrong then it's her last ride home. That knock comes straight from lower crankcase, not cylinder head. I suspected that maybe a valve is a problem but stethoscope shows diffrent. I have watched also some honda civic vids and their rod knock was exactly the same as this one.

I just need confirmation, that's all. I would need to trace another bike like this and take it's engine. This one had 90839 on odo. Probably rebuild is way out of reach because I would need new set of cylinders/pistons/crankshaft which are not existing as new. I can swap rod bearings for new ones, new gaskets but I assume it's just trying to heal the dead in the grave.

[Nessism]

Hard to say from the video but I'd start by pulling the valve cover and checking the valve adjustment. Assuming that all checks out then I'd move to the cam chain tensioner and the chain guides, to the extent you can check them anyway. If that checks out I'd move to the starter clutch next. The rollers and spring plungers sometimes launch. And lastly there is the clutch as you mentioned.

BTW, the engine seems to be running poorly in the video. Is it firing on both cylinders? Something seems off...

[Himer]

It does. Officially I have given up carburetors battle, there are 4x BS26SS - no one has parts for them and right now I am just taking wrench from pocket of my jacket and I hit it with wrench to stop overflow. I have polished needle valves and their heads to no avail, it still overflows after setting 21 mm float level. Officially I am done, it did take new jets, new diaphraghms, new needle valves new needles, new pilot jets etc. I spent enought money and SHOULD work goddammit. It runs like crap and what's left I want to do is to open throttle and let it destruct itself it deserves nothing more anymore. I took carburetors apart 5 times and that goddamn piece of **** still overflows.

[GregT]

GSX400F - air cooled four with a plain bearing crank and rods. Designed by the same team who did the first GSX750 16V engine with it's known lubrication problems.They were sold here - and got a reputation for spinning big end shells. Very few survivors now. Almost certainly, that's what's happened to yours.The 750 got sorted to an extent. The 400 didn't, the next model was watercooled and head and shoulders better.

[Himer]

GSX400F - air cooled four with a plain bearing crank and rods. Designed by the same team who did the first GSX750 16V engine with it's known lubrication problems.They were sold here - and got a reputation for spinning big end shells. Very few survivors now. Almost certainly, that's what's happened to yours.The 750 got sorted to an extent. The 400 didn't, the next model was watercooled and head and shoulders better.

This one lasted for 90k kilometres. Well it somehow sorted itself out. Bad carburetors as a whole part BS26SS CV are little nightmares to get them running. Even with working carburetors this model lacked power and worked funny when trying it to the end of tachometer, it worked best on half of tachometer scale. I am going to remove it's battery and storage it properly. For nor I am going to buy next bike and when the time comes I'll disassemble this engine and swap shells for new ones. It had numerous oil leaks anyway so a last chance rebuild will help a bit. Maybe I'll be lucky and I'll find engine in a good shape with better set of carburetors to toy with. I checked tensioner, starter clutch and well, nope. None of that. Stethoscope says knock is coming from bootom of the engine and I guess cyl 1 or 2 is the problem. Maybe no suzuki next time to ride with? I had GS 500 for a while - crankshaft seized. I had GSX 400 F for 3 years, now the engine is pile of junk.

What is more funny is that I have checked oil pressure every maintenance job and it was within the spec. I have even used fully synthetic oil to make it last more. I never had luck for motorcycles I guess. Maybe I shuld buy brand new one from the dealer next time.

[Guest]

This one lasted for 90k kilometres. Well it somehow sorted itself out. Bad carburetors as a whole part BS26SS CV are little nightmares to get them running. Even with working carburetors this model lacked power and worked funny when trying it to the end of tachometer, it worked best on half of tachometer scale. I am going to remove it's battery and storage it properly. For nor I am going to buy next bike and when the time comes I'll disassemble this engine and swap shells for new ones. It had numerous oil leaks anyway so a last chance rebuild will help a bit. Maybe I'll be lucky and I'll find engine in a good shape with better set of carburetors to toy with. I checked tensioner, starter clutch and well, nope. None of that. Stethoscope says knock is coming from bootom of the engine and I guess cyl 1 or 2 is the problem. Maybe no suzuki next time to ride with? I had GS 500 for a while - crankshaft seized. I had GSX 400 F for 3 years, now the engine is pile of junk.

What is more funny is that I have checked oil pressure every maintenance job and it was within the spec. I have even used fully synthetic oil to make it last more. I never had luck for motorcycles I guess. Maybe I shuld buy brand new one from the dealer next time.

You must ride these bikes hard and red line alot to have all these crank issues. I don't know for sure, but with the availability and what I've thought of as a very dependable engine, I'd look into putting a GS500 engine in it. At least parts are available and also performance mods.

[GregT]

You must ride these bikes hard and red line alot to have all these crank issues. I don't know for sure, but with the availability and what I've thought of as a very dependable engine, I'd look into putting a GS500 engine in it. At least parts are available and also performance mods.

I'd seriously doubt a 500 twin would fit. The GSX400F is a small four which is quite short vertically. The 500 twin isn't short...
Look where he is too.

[bwringer]

Badly unsynchronized carbs or an ignition miss can create all sorts of terrifying engine noises.

Basically, anything that causes uneven power pulses will cause mechanical noise.

May or may not be the issue in this case, but it's common.

[Himer]

Badly unsynchronized carbs or an ignition miss can create all sorts of terrifying engine noises.

Basically, anything that causes uneven power pulses will cause mechanical noise.

May or may not be the issue in this case, but it's common.

Nope, unscrewed spark plug, fitted long screwdriver in the chamber and took crank for a spin with 19mm. Cyl 1 big end is loose I feel and hear knock when pushing on a piston. This engine is officially dead. I could try to fit there engine from 750 or 1100E. Similiar size.

About hitting redline. Looking on all 3 years I had it I barely hit 9k mark. Sometimes redline, but very rare I wasn't pushing it to the max. Usually I kept between 3.5k to 6k. It's the motorcycle which corners badly so you're not going fast with it especially havinng drum + wery weak front non vented discs.

[Grimly]

You must ride these bikes hard and red line alot to have all these crank issues. I don't know for sure, but with the availability and what I've thought of as a very dependable engine, I'd look into putting a GS500 engine in it. At least parts are available and also performance mods.

The four-cylinder GSX400F was widely sold in Europe and became notorious for running big ends on the crank, which was rather disappointing as it was trading on the bulletproof reliability record of its predecessors.

My friend had one that did exactly that. Luckily, we also had a GS550 / 4 -cylinder engine available, and fitted it instead.
It does fit, with nothing major needing done, just using a mix of bracketry from the original and the replacement engines.
I unrecall whether the airbox fitted, but I don't think so, so it would have ended up with filter pods.