View Full Version : Gearbox problem?

14th September 2008, 11:53
This is on a 1988 Honda GL145 which I'm slowly sorting out the problems on. Whilst madly saving for a new bike!

Basically when I go for a ride, once it gets up to temperature, (usually 5km or so of riding) I hear a 'whirring' noise coming from the gearbox, makes a noise in 5th, 4th, not so bad in 3rd, silence in 2nd and a slight whir in 1st. Still changes up and down fine with no excessive crunches etc.

Is this possibly oil related, and if so, how do I change it and what should I use (have a spare bottle of Castrol VMX at home!)

14th September 2008, 14:34
That is, if it is even seperate to the sump oil? :no: Damn I would love an owners manual/workshop manual!

18th September 2008, 22:05
GL145 will surely all be in the same sump, shared gearbox and engine oil. I don't think small 80s thumpers like ours are particularly picky on what they run on, anything you get these days has to be far better than what they had back then. Just keep it topped up and change it often :D

I would guess that mineral oil would be better -- people say that synthetic oils don't like the rubber seals in old bikes. Diesel oils are cheap and suitable (apparently better than car oils, which are supposed to have additives that cause clutch slip); very similar in makeup to motorcycle-specific oils (which are a rip-off and a half). I use Delo 400.

Doing an oil change (and then following with another after a couple of thousand kms!) surely can't hurt, dunno if it'd fix the problem though. I have had a top-gear `whir' since 30,000-40,000kms ago on my RS. I wonder if it might be the hardening on the gears wearing through, on a suggestion from a few people. The gearbox has been fine (especially top gear) up until now; just recently 1st gear seems to be making a bid for freedom, but there was no whir or whine ever in 1st.

18th September 2008, 22:24
Diesel oil in a petrol engine!, good god man are you insane!, your engine aint gonna last long.Diesel oil is a detergent oil which will totally fuck a petrol engine.

18th September 2008, 23:36
Diesel oil in a petrol engine!, good god man are you insane!, your engine aint gonna last long.Diesel oil is a detergent oil which will totally fuck a petrol engine.
Plenty of people with a hell of a lot more experience than me on here have been doing it for hundreds of thousands of kilometres. All over the internet you'll see recommendations to use `Rotella', especially during break-in period for some reason -- Rotella is a popular diesel oil. Here's a quote from Wikipedia (http://en.wikipedia.org/wiki/Shell_Rotella_T#Motorcycle_usage):

Motorcycle usage

Though marketed as an engine oil for diesel trucks, Rotella oil has found popularity with motorcyclists as well. The properties of heavy duty engine oils tend to map to the same requirements of motorcycle oils, particularly those whose engine and transmission share the same oil. (This is called a "shared sump" design, which is unlike automobiles which maintain separate oil reservoirs - one for the engine and one for the transmission). The chemical additives found in heavy duty engine oils work well with motorcycles. In addition, the lack of "friction modifiers" in truck oils such as Rotella means they do not interfere with proper wet clutch operations.

Though not yet officially announced by Shell, posts in various motorcycle-related forums cite e-mail confirmation from Shell that Rotella 15W-40 CJ-4 has been tested and shown to meet the JASO-MA friction test. This particular certification is important for motorcycles because of the clutch design which is bathed in the engine oil. This is known as a "wet clutch." Oils that have excessive "friction modifiers" tend to make wet clutches slip. Indication that Rotella T Triple Protection passes the JASO-MA friction test offers one more reason to seriously consider Rotella T for motorcycle use.

Motorcycle specific oils tend to cost between $8 and $10 per quart. Shell Rotella T 15W-40 costs about $10 per gallon (or about $2.50/quart). The price economy of Shell Rotella T allows a motorcycle owner to change oil more frequently, thus matching the "extended change interval" value of motorcycle specific synthetics.

Diesel oil is very, very similar to oils labelled as motorcycle oils. Which are also packed full of detergents.

Look on the back of most diesel oils -- says there, `suitable for diesel engines and gasoline engines'.

19th September 2008, 06:04
Diesel oil is just fine for bikes (four stroke ones, anyway).

Straight mineral will be just fine for a GL145, it's not a demanding environment.

THis whirring. have you asked an experienced biker for an opinion ? Especially one with experience of older bikes.

Motorcycle gearboxes use straight cut gears, they won't (usually) be as quiet as car gearboxes. Some models, gear noise is normal. It depends of course, on how loud it is and so on, hence getting an opinion from someone experienced. Quite often novices get unnecessarily alarmed about noises from motorcycle engine.

Your post seems to imply that you are not sure if the oil level is correct. *That* is important.

Normally (I'm not familiar with the GL145) there will be either a dipstick attached to the oil filler plug, or a little plastic window in the crankcase. Hold the bike level and vertical (important, that), and check dipstick, or check that the oil level is half way up the window.

To change , there will be a drain plug in the bottom of the engine. Remove plug, drain out old oil, replace plug, pour in correct amount of new oil. Changing the oil filter would also be a good idea, but the details of how to do that are too model specific for me to comment.

21st September 2008, 10:10
I've found a workshop manual for a Honda CB125 and it looks pretty similar in terms of dipstick etc. so for just general maintenance I'll be using that. Delo 400, is that an oil you can get at supercheap/Repco?

Cheers, I don't really have an experienced biker to show at the moment, my Dad has only ever owned new bikes so the noise is a mystery to him...Any volunteers in Nelson?!

21st September 2008, 10:58
Yes Supercheap have Delo oil (up here anyway)

21st September 2008, 12:38
I've found a workshop manual for a Honda CB125 and it looks pretty similar in terms of dipstick etc. so for just general maintenance I'll be using that.
Er, just be careful with that -- there's a quite few CB125 twin-cylinder models around, which will be very different from a GL145 single-cylinder motor. I've no idea if the CB125 singles were related to the GL145 either, but wouldn't be surprised -- plenty of bucket racers seem to be using engine parts from all kinds of Honda CBs, GLs, XRs and throwing them all together.

I'd ask here on KB if anybody has an electronic version of the GL145 manual. I'd be surprised if there wasn't; Loncin manufactures a very popular 150cc copy of the motor, and the Chinese manufacturers normally make the manuals available free of charge on the net.

Here in Auckland you can get Delo 400 at The Warehouse too.

21st September 2008, 14:45
it too could be bearing noise, not sure if they are ball or roller bearings, also prior to refill of fresh oil..try an additive too.. lucas or moray's.. come in oneltr..
if noise is reduced after oils been add then may well have bearings to replace..
as youre not said that changing gears cause any prob's.. so i'll say its a bearing or roller bearing ... whirring..and yup Nothing wrong with Desiel oils..

22nd September 2008, 11:10
No Delo 400 at supercheap, will continue the search, the CB125 is a single with the option of a covered chain :sick:, if someone has an electronic copy of a GL145 manual I would dearly love a copy. I'm hoping it's not bearings as it only happens when the bike has been running for 5km +

10th October 2008, 11:54
Oil changed with Delo 400, seems to be loving it, but still got the gearbox whir, does that mean it's not bearings?! I think this needs an experienced rider to diagnose!:yes:

10th October 2008, 12:36
gearbos wirr
I just changed my exhaust, I can hear my gearbox now,
sounds like a DC3 comming in for a landing!
But I have only just fitted new bearings to it, had it apart last month, the wirring is the straight cut teeth singing merrily as they go about their business.
I would think that is your noise as well.
If it was bearings, you would get an associated clunck with each gearchange as the slack was taken up, very noticable.

Diesel oil, yeap been using it in my bikes since way back then, better to use in my opinion.