Issues already =(

[SpannerMonkey]

Okay, So it turns out my Suzuki GN250 wasn't as good a condition as I first thought.
Air filter was torn and has bugs, mud, and bits of sweet wrapper in it, as well as the screws holding the airbox cover on were RUSTED on to plastic (Which says to me it hasnt been touched for years)
oil is thick, black and below the limit (Topping up asap) which also says to me oil filter hasnt been changed in ages.
Plug isnt too bad but is a bit whitish so going to go for a colder plug
I doubt valve clearances have ever been checked let alone adjusted.

The bike at the moment HAS done 80mph on the motorway downhill
but on flat I can get 72-75... with a passenger it will SLOWLY creep to 70 but a slight hill slows it to 60.
Reckon a good service will help it a lil? =P
I'm hoping for 75 with a passenger and 80 solo on flat... But maybe I'm being optimistic
the bike has done 16,000 on a '90 plate and the clutch friction plates are about to be changed (As the clutch is slipping when I change gear but grips after 2 seconds)
What else would you say needs doing?
Anyone local in the west midlands who could do my valve clearances? =P I've been quoted 35 quid at a garage for a 4 valve single, is this an okay price?

[Digit]

A bit slow, but that could be down to needing sorting.
Well it's a four valve head so I suppose £35 is reasonable in today's prices, but DIY is much cheaper.

Roy.
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Happy daze!

[Blau Zedong]

[SpannerMonkey]

[SpannerMonkey]

[Digit]

Yep! Know the problem SM.
I've never managed to do tappets by turning the rear wheel, I always turn the crankshaft.
£35 will buy you the necessary tools to do that.
As reguards the feeler guage there are ways and means. On a lot of guages the case can be unscrewed and the appropriate feeler removed, this will normally help prevent the slipping. Otherwise cut the feeler out and keep it.

Roy.
____________________
Happy daze!

[SpannerMonkey]

[Digit]

Take it from me my friend, doing it properly and taking it to a garage are not always the same thing!

Roy.
____________________
Happy daze!

[SpannerMonkey]

Just a bit of good news, With regards to my oil, I was doing some research and car oil in bikes causes the clutch to slip (Bikes being wet clutch, cars being dry) the person who owned the bike before me is DEFINATELY the type of person to put car oil in it and probably the wrong grade at that =P I'm gunna get me an oil and filter change. See if any clutch is restored =D

[Robby]

Unfortunately your research is bollocks. The only car oil known to make wet clutches slip is Castrol Magnatec. Lots of us on here have done thousands and thousands of miles using car oil with no ill effects.

However, not enough oil that is totally knackered can cause all manner of problems.

[SpannerMonkey]

Read up robby =P
https://en.wikipedia.org/wiki/Motorcycle_oil

[Robby]

Try a few years of experience instead.

[Ichy]

The GN250 has been around since 1982, do you honestly believe that anyone cared what oil they used back then?

Marketing is a wonderful thing why pay £3 a litre for general engine oil when you can get extra special motorbike oil with added win for just £10 a litre?

[tahrey]

Interesting ... dare I take that leap?

... maybe when the 4L bottle of Fuchs is used up anyway.

Magnatec is nasty shit, at least according to a couple other guys I've heard talk about it before, one of which was a BSc chem working as an oil tech. Wouldn't be worth using at all if it wasn't for the supposed fancy stuff. Unsurprising it'd ruin your clutch.
(all oil is chock full of polar molecules btw - that stuff that "sticks... like a magnet". it's why it's slippy but hard to get rid of without (opposite-pole) detergent)

My other reading however suggests up-to-date car oils have friction reducing things in and that's why they're contra-indicated for shared-sump bike engines/clutches? The bike formula is actually more primitive... which does sort of add an extra "f***-you" sting when you consider it costs more.
1982, that sort of stuff hadn't even been dreamed of. Most cars still ran on 20w50 full-mineral FFS.

Also I've had 79 on the clock downhill on my 125, and 70 or more on the flat, so I hope your performance improves noticably once you've tuned up ... or you were using GPS

PS if all you need to turn the crankshaft is some kind of socket bar or rachet, a suitable socket or bit to remove the crank cover, and another to fit on the shaft bolt, I'd feel right ripped off at paying £35 for all that. £20 all in I'd say, and that's buying them from Halfords, which ain't cheap - but serves a need for emergency purchases.

[Kickstart]

Hi

Another vote for car oil rarely causing a problem with clutches on bikes.

Certainly at least 3 of our bikes have car oil in them now without any clutch slip issues. Have used fully synthetic car oils without problems as well (currently using a Rock Oil 10W40 semi synthetic).

As to the valve clearances for the GN, they appear to be 0.03~0.08 inlet and 0.08~0.13 exhaust (all measures in mm). 0.04 seems a bit close to the min inlet clearance.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[evoboy]

+1 on car oil.

Never had an issue. Currently using 20w50 Morrisons own brand in the gearbox of the X7 and Castrol GTX in the ZX6.

Seems to be alot of marketing crap in the bike world.
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Suzuki GT250 x7------- Fazer 600------CB250RS------Aprilia Rally 70----- Bandit 600

APT Motorcycles

[SpannerMonkey]

[SpannerMonkey]

[nowhere.elysium]

[SpannerMonkey]

[SpannerMonkey]

got 5 litres of semi synth 10/40 oil and a new oil filter, Changin it later on tonight. Got a good 45 mile each way jaunt tomorrow so we'll see how the bike takes to it.

[SpannerMonkey]

Oil filter and oil replaced, new spark plug too, carb cleaned.
Clutch getting worse, ONly about 200 mile left in it lol
When you replace a clutch do you replace ALL the plates? or just the friction ones?
Also, Do i need the new clutch springs or will my old ones do fine?