crank shaft oil feed? low oil pressure

Hi folks I have done a big rebuild on my Xr6 and since then had problems with it overheating. There seems to be too little oil reaching the head, (lots of bubbles and fumes not much oil) and I have burnt out a set rockers.

I have checked all oilways and seals thoughly, everthing is clear and clean. Tried new oil pump and yes I did remember the little dowls and o rings behind and the in front the oil pump, no better.

Any ideas I tried everything I can think of?

One suspect, I checked the crank shaft and it seems that is has almost no back pressure. I can imagine that the hot oil might choose to go this way rather than up hill to the head. Sound plausible?

Should there be some resistance? Is there something in the crankshaft that restricts the oil flow or is it just the size of the oil hole in the carnk pin. I had a new crank pin and con fitted is it possible that the workshop could have fitted the wrong pin. I can tear down the crank, but its a big job. Can anyone tell me how big the hole in the crank pin should be so I can check it once it's out.

Any help much appreciated I am at the end of my teather.

Just a few things to think about if you haven't already. Is the crankshaft end seal in the right sidecase facing the right way? The apex of the seal should face the oil pressure. Also the cam seal on the left bearing should face out, away from the camshaft center. I don't know if you changed the cam but make sure there is an end plug installed. When I rebuilt the top end on my 650L and when I change the oil, I loosen the oil line a bit where is goes into the head place a rag under it and crank the engine with the ignition off (electric start) to make sure the pump is primed and filter is full and oil is flowing to the top end. Then tighten it before I fire it up. The oil system also feeds the transmission (unfiltered) so check the alignment of that oil tube and o rings. This tube bends easily and could come close to the pump drive gear which would be bad. I have heard of the oil lines that come from the frame getting twisted during install limiting oil from the tank. I am unfamiliar with the crankshaft on this engine, but I would think if the passage is clear it would be better than not. Call the shop that installed the rod and ask some questions. The machinist should be familiar with this crank.

Check the oil line between the frame (where metal screen oil filter sits in the frame) and the engine cases (oil pump).Maybe the line is twisted,a friends XR600 had the same thing, worn rockers etc....The line was twisted after he cleaned the metal screen. :applause: So non or little oil flow...

Thanks SDBSKI. and XRMANU, all good suggestions. Unfortunately I already checked all these possibilities. Seals and oil lines all good, and I primed the pump. Before starting I checked at the banjo bolt where the oil line enters the head and oil does arrive, but once the engine is hot this feed contains lots of bubbles and fumes.

Tearing out the crank is a major step so I tried everything else I could think of first. But if anyone else with good ideas please tell me. I keep thinking it's something small I forgot to check.

I just measured the con rod side clearance (between the con rod and washer) and it was well outside standard. It measured 0.75mm and standard is 0.05 to 0.50mm. I guess this might contribute to the loss of oil pressure However this alone is not enough to explain the problem as the service limit is 0.8mm. It does suggest that the guys who assembeled it were none to careful. I will press it back to the minimum setting.

I tried to contact the workshop that did it but get no reply. As you may have spotted I am in Africa (great off road riding here if your bike works, but a long walk to the nearest garage when it doean't;-) I wanted this job done well so I sent the crank to a workshop Holland (wish I hadn't now) maybe SDBSKI would like to pay them a visit they are just next door (Joke!)

Still trying to think of something but if I don't get a culprit soon I will press apart the crank to check the crank pin. I will start a new thread to look for the correct dimension for the hole in the crank pin.

Is the metal screen in the frame clean? Brass/metal shavings etc??

A shop in Holland did your crank? I'm from Belgium..

yep the screen did have bits of brass in it when I first stripped the engine, but I cleaned everything when I rebuilt the engine and now its spotless. As is all the inside of the engine.

I spotted you are in Belgium, from all the way out here (africa) that seems like nextdoor to holland ;-)

Tomorrow morning I will press out the crank pin, looking for the dimensions online now.

Thanks again for your interest

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