transmission oil level 1987 Yamaha QT50??

Hi Everyone,

I just bought a pair of 1987 Yamaha QT50s. I bought them from the original owner. They have been in storage for 30 years. They both have less than 100 original miles on them. I cleaned them up, had to remove and clean the fuel tanks, replace the fuel switches and replaced both carbs....the carbs ran fine...i just wanted to get the entire fuel system taken care of. My question is how much oil goes into the transmission? I have read the manual and seen the print on the outside of where the oil goes. It's say's 30mm3? That’s a little more than 10 ounces. The only reason I question this is because you cant check the fluid level so I decided to change the oil in both. They both had 18 ounces of oil in them? I doubt the original owner added or even messed with the trany oil? I'm thinking this was from the factory? I put oil in the first bike at 10 ounces. It seems to have a whine to it that wasn't there before? I want to make sure whats right before I get these bikes on the road. Any Advise? Thanks, Jim (edited)

Re: transmission oil level 1987 Yamaha QT50??

You are correct!

The owners and shop manuals for the QT50 are here.

The manual calls for 300 cm^3 of 10W30 when exchanging the fluid, which is indeed about 10 fl oz. If the motor is dry (from a rebuild, for example), it calls for 350 cm^3, which is about 12 fl oz.

Re: transmission oil level 1987 Yamaha QT50??

Congrats. To save future pain change out the crank seals now. Engine will suck trans oil on the right and air on the left. Never run right and possibly seize.

10 oz of motorcycle oil only. I've got 10-40 in mine.

https://qt50.net/ Go here, best on the internet. Jack who is on here has ALL the info. Read all the links. (edited)

Re: transmission oil level 1987 Yamaha QT50??

Personally, I would clean and put the original carbs back on. The cheap, Chinese carbs are a crapshoot. I’ve run both on my QT’s and the original is more consistent. I second the thought on changing the crank seals, especially since you’re draining the trans oil anyway. Post some pictures of the bikes.

Re: transmission oil level 1987 Yamaha QT50??

I wouldn't touch any Japanese seals until they prove themselves bad .

My '84 Suzuki FA50 has all original motor seals and still running strong . I do have to replace the final drive seal on the rear axle .

My '89 Yamaha XT 350 has all original seals and shows no sign of any level of failure .

It should be noted that I'm not an easy rider . I enjoy pushing my bikes to their limits .

Seems to keep them from clogging up . (edited)

Re: transmission oil level 1987 Yamaha QT50??

Jack Rutherford /

Wow PD, I’m gonna guess you are the original owner of both those bikes and they have been ridden on a regular basis? And both bikes have not been performance modified?

Re: transmission oil level 1987 Yamaha QT50??

I'm kind of with PD on this, but in the case of these bikes, with such low miles and sitting forever..it's 50/50 in my book as to replace seals, my Hobbit needed 1 back in '98, the other is og and going strong, but my bike had sat with 270 miles on it for yrs...Japanese stuff, especially old Japanese stuff was incredibly well made, I would try and run it first, and yeah, second using an og carb vs chinese clone. most are garbage. Be careful using synthetic oil in older machines, seals were not made for the thinness for lack of a better word and it can leak where dino oil will not. Take baby steps and they will come back to life nicely, very little was a precision made as old Japanese motorcycles and mopeds, they took extreme care of even low end machines. That Yamaha engine is a TANK. Treat it as it was designed to be and it will last you a lifetime. Download and follow the service manual, it's long, involved and very dry reading, but if followed you will have a reliable machine for as long as you choose to own it. Best of luck with your resurrections! Always run a good battery in your QT's, it will run without, but will fry the charge coil.

Re: transmission oil level 1987 Yamaha QT50??

> Jack Rutherford wrote:

> -------------------------------------------------------

> Wow PD, I’m gonna guess you are the original owner of both those bikes

> and they have been ridden on a regular basis? And both bikes have not

> been performance modified?

Ha . You're pretty close Jack . Other than original owner , you're right .

I bought both from the original owners and both never had the lower ends apart , according to those owners . I believe both were truthful . I'm pretty sure that I was the first to have been under the side covers of both bikes . (edited)

Re: transmission oil level 1987 Yamaha QT50??

I misstated about my XT350 above .

I did replace the original valve stem seals with viton seals , as the valves needed lapping to insure the best seal there .

Re: transmission oil level 1987 Yamaha QT50??

I have an 84 that I'm not tearing into until it breaks.

Re: transmission oil level 1987 Yamaha QT50??

Jack Rutherford /

My first qt had a bad seal(s) and that had me chasing my tail until I finally broke down and changed the seals. After that, I just changed them on all future qts as a habit. I guess if it’s not burning trans oil the right side seal is fine. A leak down test would probably be the way to check the left.

Which reminds me - drain oil before shipping engines. Oil will leak out weep hole onto cardboard box. Wet cardboard is weak cardboard which tears. It’s no fun receiving an oil soaked, torn up box and most of an engine. (edited)

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