idle curiousity - trying to find what model my father had for 2 stroke yamaha 500

[seanarthurmachado]

Hi everyone,

When I was a kid my father had a two stroke street bike (a standard) which was a 500cc bike.

When trying to search everywhere I cannot seem to find the model he had. My parents have both passed away (him over 20 years ago) so I cannot ask anyone.

(Before anyone has me check for model numbers,the Motorcycle is LONG GONE decades ago, there are no pictures of the motorcycle left to me.)

I know the motorcycle was a "Yamaha 500" and had DOHC on it. I know it was a 2 stroke because as a kid when I would ride with him he would put oil in the gas, and the two of us had a discussion about why he disabled the auto oiler to pour in 2 stroke oil at every fill up by hand -the answer being "just because".)

this would have been purchased new in 73 or 74, or at latest 1975.

searching Yamaha websites, google and bikez.com reveals nothing.

sean

[Big Rich]

Well, the "DOHC" raises a problem. It stands for Dual Over Head Camshafts, and to my knowledge no early Yamaha 2 strokes had camshafts.

I do believe that it was a 2 stroke though with the other details provided.

[GS1150Pilot]

A punched out RD400 with a bit of imagination regarding the actual final displacement?

[seanarthurmachado]

Nope. Definately a 500. I remember seeing the side cases stating "500" but I cannot remember what letters, and as a 5-9 year old I never asked the year.

I vaguely remember him telling me that "Most people start on a 250CC but I started on a 500CC".

this bike would have had a rear drum but I clearly remember the front disk brake.

The engine was air cooled, with both kickstart and electric start, chain final drive (it fell off once during a ride and he had to stop and oil it.)


sean

[GS1150Pilot]

What era would this have been? '70's, then? If so, I don't think Yamaha had a road-going 500 2-stroke. In the 80's, there were a few RD500's out there on the roads, but those were very modern and not what you have described (fully faired, all disc brakes, etc.)

[seanarthurmachado]

This would have been mid-late 70's.

My mother used to always tell me that when 1 was about 2 (I was born in 1972) she and my dad separated, partly due to the motorcycle. (mid llife crisis, trying to ride with a club, party all night long when he was in his 40's instead of his 20's.) While they were still together he bought the bike new.

[8ball]

XS500, or TX500 (actually they are the same bike)...both DOHC, but neither a 2-stroke. Yamaha did not make a 500cc 2-stroke in that time frame. 2-strokes do not have cams, and as stated, DOHC stands for "Dual Over-Head Cam". Well not 2-stroke gas engines. My locomotives have 2-stroke diesels, and they have dual overhead cams, but they work differently than a motorcycle engine, and requires forced induction (turbo or blowers) to run.

[GS1150Pilot]

That was my thought, too. Perhaps he added Marvel Mystery Oil to the gas?

[steve murdoch]

Suzuki T500 Titan got a disc brake in '76 and became the GT500.
Are you sure it was a Yamaha?

[Guest]

I'm going with the XS500 too.

Here's a pic of a late 70's model

http://www.motorcyclespecs.co.za/model/yamaha/yamaha_xs500%2078.htm

Yamaha never made a 2-stroke 500 until 1984 when it produced the RD500LC.

http://www.motorcyclespecs.co.za/model/yamaha/yamaha_rd500lc.htm

DOHC (Double OverHead Camshafts) means that it wasn't a 2-stroke but 'disabling the auto oil feed' means it didn't have any camshafts at all. Something's gotta give.

I know it's a long time ago and memories get mixed up, hope you find what you're looking for.

[Buffalo Bill]

Sounds like Dad was skeptical about the new 4 stroke, so he kept his 2 stroke habit for oil in the gas.
The human mind is full of superstitions.

[seanarthurmachado]

I clearly remember the 500. I am wondering about the dohc. Could be a corrupted memory. But the bike was a two stroke. One of my brothers (since passed away) mentioned how the old Yamaha had over 100k on it, a lot for a 2 stroke.

[bwringer]

So does this picture of a TX500 look familiar or not?

It matches every aspect of your description except the idea that it's two-stroke. Again, DOHC means camshafts, which were decidedly not a feature of two-stroke engines. The TX500 was released in 1973 -- my uncle had a purblue one just like the picture. Very handsome bike, and a great engine. However, the engine had some design flaws so very few made it to high mileage.

You might also check Youtube for some RD/RZ 350 and 400 videos to see if the 2-stroke sound seems familiar. Perhaps someone put "DOHC" on the side covers as a joke.

Also, the belief that you had to add oil to the gas even for four-cycle engines was common at that time. When unleaded gas became available, many people thought that their Japanese motorcycles needed oil in the gas to keep the valve seats from wearing. IIRC, Japanese bikes had actually used hardened valve seats and had been able to use unleaded since the 60s.

If it's definitely not a TX500, then the only real option for a 2-stroke Yammie of that era would be the RD350 (1973-75). In other words, some aspect of your recollections is off-base. I think a few Youtube vids of RD350s featuring the distinctive sounds of stock and aftermarket exhausts would settle the matter pretty quickly.

You mentioned disabling the auto-lube, which was very common for RD owners to do at the time (when it worked, it was fine, but IIRC it was a fiddly vacuum-operated widget and few people trusted it for long), so that's another vote for the RD350. And the fact that it made it to high mileage. Very few TX500s survived, but the RD was darn near bulletproof, especially if it was ridden on the street regularly and not raced, crashed, or modified excessively.

[seanarthurmachado]

That bike looks almost exactly like it except for the vents on side covers. One thing comes to mind...my father mentioning that he ordered a bigger engine for it. I was assuming that was his way of telling a 5 year old he got the bigger engine option that was standard.

I'm wondering if this was some sort of oddball request that the dealer did with his bike on order.

I seriously doubt he did an engine swap. The most I ever saw him do was once try to change a tire on the front to avoid a shop fee....also I vaguely remember the bike riding strange (bogging then pulling hard and racing) and he mentioned it needed a valve adjustment...and me asking why he didn't do it and he said it cost money to do at a shop he didn't have , and the tools to do it himself were too expensive.

[bwringer]

If it had valves, it definitely wasn't a two-stroke bike.

Here's a video of an RD350 with stock pipes, just to show you the distinct sound. Big bore kits were common for these.

https://youtu.be/r1uFnwDbRhw

Here's a video of a TX500 running -- very different sound. Also note that it had an electric starter -- the RD was kick only:

https://youtu.be/ogkkL9vrza4?t=6m1s

I don't know that anyone ever had big bore kits for the TX500 (again, the engines usually grenaded early) but there was a TX750 model. The side cover vents were black and not as visible, but they said "OHC" (Over Head Cam) instead of "DOHC" (Dual Over Head Cams).