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1979 Yamaha TT500

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So, my neighbor buys this bike at a yard sale.

But, it's not the bike he really wants.

So, I end up with it.....

At first, couldn't get her to start.

Thank God for Google and documented starting procedures....

Follow the procedure, starts right off.... amazing!

Most of the time, she fires right off. First or second kick, tops.

Sometimes smokes quite a bit, then calms down, sometimes no smoke.

However, somewhere in the mid-upper rpms of third, she starts missing....badly. In some ways that's ok, its about the same time I run out of usable dirt or the road I aint supposed to be on! 👍

Have yet to hit forth,

Today, fired her up, but failed to warm her up, ran about fifty yards, and quit. Would not start.

Checked points, cleaned and reset, checked plug / spark, cleaned and reset.

Cleaned airbox and filter. NO GO, Wont start.

Finally started again after really, really cleaning plug of all residue.

Smoked a little, settled down,, Ran smoother.... but again, hit third gear, get near half throttle and the miss appears.

After this, let her sit for awhile, four or five hours, started right up but smoked just like I'd thrown a bunch of sea-foam in her.....

Should mention, spoke to the prior owner this evening, sounds like the bike has sat more over the last two years (the time he owned it) than anything else. Would like to keep her and lean her toward the XT side for round a bout road use.

Ideas on the miss, the smoke?

Any and all help greatly appreciated

lar

bent axle

btw, will try to get some pics up tomorrow.

thanks

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You should try a brand new plug, cleaning them doesn't always work. As for the smoke, mine smokes quite a bit but it has a bad head gasket. it could anything from worn rings to bad valve seals. the miss may be off timing or an air leak somewhere after the carb.

i am not super experienced with motorcycles yet but, hopefully this will help to get you started.

good luck, man

Edited by erniez
bad grammar

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In digging deeper on the net, I believe it is a 77.

Thanks for the info, hope to get some work done on her soon.

102_3234.JPg

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hmmm....forgive me if im wrong but the misfiring could very well be the advance/retard settings on the points....i had a xt 500....frigging amazing bike but like you said hit mid throttle and she miss fires.....so try this on the points plate(im not really sure of the correct term for it)loosen the 2 or 3 screws and turn the plate a bit...either to the left or right, try start the bike and give it a try then if it gets better turn it some more(small amounts are best )if it gets worse turn in the oposite direction.........BUT use a marker to remember the position it runs in....coz you will be extremely mad if you move it then think...FLIP....hopefully that will help...also not sure if you cleaned the carby but there may be dirt etc in the jets starving it of fuel...... as for valves etc...yep very likely but try eliminate the simple problems first...have fun and be patient these old bikes can be...............interesting 👍

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Thanks for more info.

Aside from the miss and crop dusting, she is in pretty good condition.

The internals of the headlight are all busted up, the tail light lens is missing.

Just ordered a kickstand spring off ebay. It is frustrating trying to hold the bike up while bending to attach the PO"s supplied bungee chord.

The seat cover is almost toast. I say almost, because there is enough of the original material left for patterns to fabricate a new one.

Tank has a few dents. Obviously, the aforementioned is only cosmetic and has very little to do with how it runs.

I have yet to give her a bath. Been hesitant to take her to the car wash and blast high pressure water on what could be a marginal wiring harness.

Nor have I cleaned the carbs, or tank internals.

Have yet to procure a manual. Hesitant to do to much without one.

Anyone have any luck with the digi versions available?

Stevo, I will check the "points plate" and adjust accordingly.

Oddly, when cleaning the points, had a sense, something was remiss there; Dare I call it zen....

As things are, will probably be attacking the simple stuff first anyway.

Thanks again

another view

102_3211.JPG

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there is an advancer mechanism behind the points plate . They sieze up . Just take the cover off and grab hold of the points cam it should be able to be rotated freely back and forth about 20 degrees. If it doesn't move that's your problem. I would not recommend setting the points to any location other than where they are supposed to be.

If you advance it by simply adjusting the points and try to kick that thing , it will kick you back like a Mule !!

The smoking could be wet sumpping. the oil leaks out of the oil tank and down into the engine. It will smoke until it pumps the oil back into the tank. Also make sure you check the oil when it's warm . if it's leaking down into the engine and check the oil level at that point when it's cold you'll be adding a bunch of extra oil to the system ( make sense ? ) If it's not wet sumpping the rings could be stuck . Easiest way to tell that is a leak down test (google that )

Good luck with it it looks pretty nice 👍

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ah bruce.....in my rush to try help i forgot about that advancer.....lol 👍....yea that would be the first thing i guess seeing as the points generally dont move...anyways was just speaking from experience :ride:

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Like Bruce said, I would check to see if it is wet sumping. My XT would smoke some at startup and one day I started it up in the morning and started riding off and about halfway down the block it just died and would not start back up. I drained the sump and there was quite a bit of oil, I refilled the tank and it started right up! I think it was sumping and when I would start it the oil in the sump would go through the crankcase vent and into the airbox causing it to burn the oil and smoke. I just ordered the seals to fix the sumping and will be replacing them as soon as they get here. Go to sr500forum.com and search "Wet sumping". Great looking bike! Good luck!

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Today's festivities included

Checking the oil level cold.

Just below the bottom of the "F"

She did not start up on the usual 1-2 kicks.

Maybe 8-10, but did start....

Not to bad on the smoke

Rode around a little bit, warmed her up, didn't seem to miss as much,

and, wished like heck could have extended the trip.

Shut her off, and what do you know: oil level above the top of the F.

So, should I change the thread title to "Sumper Talk" 👍

Anyway, I digress

I assume the aforementioned implies the need to change the oil sump ball and seal?

And, before shutting her down, thought I was listening to tappet noise....

I read somewhere, adjusting the valves on these can be, or should be, done more frequently than the manual suggests? In other words, is the noise an indication the valves should be adjusted in the not to distant future?

Did not open the points cover to check the advancer.

Do my best to get that done tomorrow.

Speaking of that... Got a little confused between Stevo, and BruceD's comments re: the advancer plate.

I understand the rotater either moves 20 degrees back and forth, or it doesnt. If it doesn't move, what then?

I hate not having a manual

thanks again for the info and comps

lar

bentaxle

Edited by bentaxle

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If the advancer is siezed up you need to remove the points plate

(mark it before taking it off )

Then there is a single bolt on the end of the advancer ,remove that and the advancer will slide right off the shaft. you'll need to clean it and free it up or if it's really bad replace it with another. When you put it back on it only goes on one way there is a small locator pin on the shaft.

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i found these manuals a while back:

http://www.oldgitsuk.dsl.pipex.com/ThumperInfo.htm

I was told to check the following parts if the bike is sumping:

93101-14089-00

93104-11038-00

583-13113-00-00

93503-08007-00

90501-05378-00

And then the cover gasket if you need it:

3HT-15462-01-00

Hope that helps!

Edit:

These part numbers are for a 80-81 XT, I think some of them are the same but you may need to lookup the corresponding part for your particular bike.

Edited by teledan

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i found these manuals a while back:

http://www.oldgitsuk.dsl.pipex.com/ThumperInfo.htm

Rut Roh

Teledan just eliminated one of my excuses for not getting things done.

Awesome! Thanks. Some of the TT pics on the aforementioned link's pages are incredible.

Today, rainy and cold; did not feel like spending any time out in the man cave working on the bike.

Think I'll opt for sitting by the fire with a good book.

Ok, so I over state my reality: No fire, no book.

Guess a candle, a computer screen for a hearth, and a Hayne's TT/XT PDF will have to suffice.

thanks again

lar

bentaxle

I got some readin to do...

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As the others have pointed out, the motor is wet sumping. Very common and not a significant problem.

Adjust the valves, and set the point gap and timing statically as described in the manual. Then put a timing light on it and get it spot on. If you goose the throttle with the light on the flywheel you'll easily see the timing advance as it should. If not, disassemble and clean the advancer as Bruce described.

It's a simple bike to work on. The manual will make your life much easier.

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