GPZ 500S Oil Leak

[dn38416]

Hi,

I've noticed a slow oil leak from the bottom of the filter. I've changed the oil and filter on it quite a few times and had no issues. In any case i appreciate it sounds like this (https://www.bikechatforums.com/viewtopic.php?p=4276711) and will empty and re-tighten it on the weekend, might as well get a new filter.

But aside from me tightening it while it's full of oil. I've also noticed the acceleration is much less responsive especially noticeable as it struggles to climb at medium to high revs which didn't happen before - could there be something up with the oil pressure? The light isn't on, but the timing coincides with the leak.

Talking of which, where exactly is the crankcase breather hose? I can't see anything labelled as such in either the Haynes manual or the online parts diagram, would be v.useful if someone could point it out.

On a separate but still 'my bike is getting fcked' note, my brand new rear BT45 has got a massive gash in the centre of the tyre. The stone that came out of it was as least as deep as the tread. (pic to follow) what's the standard guidance - am i supposed to get it patched up or is there something i can do myself?

[stinkwheel]

If oil pressure is affecting performance, your engine is already scrap. So I doubt it's that. A mid-range hole could be a clogged or disintegrating air filter so I'd check that.

You're sure you've not overfilled it? Oil level should be between the two marks on the sight glass with the bike level. (have to ask, more than one person has brimmed their engine with oil).

If the gash is as deep as the tread, carry on, the tread is solid rubber. It's when it goes deeper than the tread you might be worried but even then, if there's no air coming out, I'd probably just keep an eye on it. You need to repair it when it becomes a hole, otherwise there's nothing to repair.

As I recall, the crankcase breather is directly under the carbs and is routed into the bottom of the airbox.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[dn38416]

thanks stink, i normally fill it just to the top of the sight glass. I'll take a bit out and see if that does anything for performance. I'm definitely getting more vibrations over 5k rpm than before, and it really struggles going from about 60-80mph.

Only other think i can think of that was different this time i changed the oil was i overtightened it a bit, but literally only about half a turn - then undone it and went back to what i thought was the correct torque - so not enough to crack anything.

[Chris45]

Oil leak from the filter "may" just be a seal issue. Check the filter and housing surface for any rough edges and make sure the filter sits square to the surface when bolting up.

I have always filled the sump to the top of the sight glass. These engines need plenty of it, but as mentioned, don't overfill it.

Poor acceleration could be a seperate issue. Is the engine idling okay? Can you blip it and hear the engine return to idle normally? If the bike is accelerating poorly at a certain range, I'd start by looking for minor splits in pipes or general carb area.

The crankcase breather is the black pipe underneath the bike, around the swingarm pivot area. These do get really clogged up and mine was blocked, which was probably another reason for some rough idling and poor running on mine last year.

My 500s had poor running last year, but I could smell the petrol! It was leaking from the fuel tap area. Always start with the simple stuff, and progress from there.

I wouldn't feel too comfy about riding a bike with a deep gash in the tyre, at speed and with the enormous stresses on the tyre. I'd bin it for my own peace of mind.

Hope the above assists, let us know how you get on.

[stinkwheel]

[dn38416]

Brilliant, thanks for that guys - looks like a lot of work to get to that breather hose. I've got a new filter now so i'll do a clean up and replace today and let you know how i get on. Might try and give the air filter a clean in the process of getting to the breather hose - but it's only 3 months old i can't think what might have buggered it.

On the tyre front i actually caught a massive screw through it yesterday so had to get it patched anyway. Will get a stop n go for next time.

[dn38416]

changed the filter and where there was a leak i found a hardened residue on the ring where the engine mates with the filter seal. I don't know if that was a symptom or cause tbh - but if the latter then that would account for why the filter didn't seat right.

Just realised the air filter requires getting the tank off, i've got a few other things to do under there so waiting for parts and will use the easter weekend.

I still quite like working on this bike, even though it takes me roughly 6x longer to do anything than a professional.

[Chris45]

[dn38416]

right, air filter is still in good shape - i've taken it out to give it a wash and re-oil (is 10w40 ok?), crankcase breather hose was clean although there was traces of oil in the part of the airbox before the filter. Maybe it's all in my head, or any other reasons for poor acceleration and a widening flat spot?

Got rid of the oil leak now as per the poor seating. And my rear tyre is going from bad to worse, picked up the second screw in under 2 weeks.

[dn38416]

update: thanks Stink, a minimal clean out of the air filter and box has produced a noticable different to the acceleration and feel of the bike.

In fact i find it a bit hard to believe how this has had such an effect - all i did was a rinse with soapy water, dry and coat with oil - then cleaned out some of the crud from the top of the swingarm while i had everything off. Was going to switch over the spark plugs as well, but they were too much of a faff to get undone and all the other stuff out the way + there's always the crud that's accumulated around the holes.

[stinkwheel]