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74tx500

newbie. TX500 problem child.

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hello,

well i'm a newbie to this forum. and well i have a 1974 TX500 i got from a guy for $500 and well since i got i've dumped around $1500 into it to make it safe and somewhat reliable(miss spelled that i know). well i pulled the engine due to low compression(should have 150psi i had 100psi with oil in the cylinders). well the head had 4 large cracks in it(i could messure them with a feeler gauge if i wanted to).

well here come the questions:

i bought a used 1977 XS500 cylinder head the one piece design off ebay with the valve cover. will this work on my older 1974 engine? and will my older carbs work on this head? i know the carbs on the older 500cc DOHC engines were junk. and i've put up with that last season. but i would like to make some kind of return on my investment with this bike.

and is there some way to make these junk carbs function reliable enough? i mean i take them a part blow air through all the passages and it still has one dead cylinder at idle. and every so offen that cylinder will cut out while riding. and it runs massively rich (i think the floats are too high).

so far this is what i've done to it:

new tires,new wheel bearings and seals, new fork seals and dust boots, new brakes front and rear, added fuel filters, MSD blaster coils, K&N air filters, luggage rack and sissy bar, highway bars with foot pegs, windshield, new drive chain and sprokets, tune-up, XS750 brake master cylinder, and rebuilt the carbs like 3 times.

well if anyone has some ideas or knowledge on these bike please help. i want to get this thing back on the road before the summer is over.

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bump!

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bump!

77xs500 heads.... those will be off the 500c, and your tx must be the 500A....

Looking at my factory manual, i dont see anything that specifically says "NO"

I looked through the yamaha engine diagrams, and from what I can see, the cylinder head assemblies LOOK interchangeable. What I mean by this is that they look like they bolt on comparably and share the same gasket. what I cant tell you is if the clearances will work out, because if I remember correctly they didnt just change how it bolted together to make it stronger, they also changed the internal shape of the cylinder head.

Here are the images.

Top is your 74 TX500, bottom is the 77 XS500

To me, the cylinder itself looks the same, but there isnt really any way to tell what it looks like inside the head. Those cracks you mention are part of the reason they changed up the design, and sometimes you can even see them on the outside of the engine. for the most part they dont affect the performance of the engine, but every now and then they become too aggressive. ive never opened up the top end of my bike, so I dont know if my 75xs500 has the cracks, but I bet it does.

Hope this helps.

75tx500.jpg

77xs500.jpg

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well there is a story behind those cracks. before i bought this lovely gem of a bike. the last owner left the old gas in it over winter. and could only get it running on one cylinder the next spring. well he got it so hot it turned the exhaust on one side blue. well that's why it's got such bad cracks.

well i bought it thinking it would be a great first motorcycle. you know learn how to fix it and then ride it. well i've done more fixing then riding. last season i put a whole 600 miles on it. more down time then up time. well i'm hoping this season i could put a lot more miles on it.

well if i can swap the newer model head onto my older bike it would be great. if it's redesigned to make it better. well that's a plus too. by clearances what do you mean? piston the head? i have new valves for the old my old head. don't know if they will work in the new head. it would be nice if i could. i plan to have a valve job done on the new head and have it resurfaced so i know the sealing surfaces are flat.

now some carb questions. i'm running the stock 1974 carbs. is there anyway to make them function better? i mean i have to futs with the idle speed screw all the time at stop lights and stuff. and if i crank it wide open in 5th gear it bogs out and slows down. i can't ride it on the hwy(65mph or above) cause it barely goes 60mph(the fastest i need to go on my way to work). i know i need to adjust the float hieght since i have gas dripping from the carb vent hoses.

well thank you guys for the help so far.

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Blued exhaust pipes can also be caused by running the bike with the choke on for too long... just a thought.

I bought my 500 with the same idea - fun ride and learn to work on it at the same time. mostly ive learned how to break different parts on it :rolleyes:

They redesigned the head to make it stronger/less prone to cracking/warping... however i seem to remember reading that they actually changed the way that the inside top of the head was shaped, and the angle of the valves looks slightly different in the pictures as well.

my thought is that they would have changed the pistons too, to mate up to the new heads. i could be wrong here. I would love to find out that i can swap on the newer (500 c/e) one-piece heads though... it would provide me with a lot more choices. from what else ive read, lapping the valves is a simple task that you could do yourself. someone else on here did a total top end job on their 400 recently, and could probably give you pointers.

as for the carbs - i have no idea what to tell you. your lack of power might have something to do with running 1974 carbs on 2008 gasoline - which has no lead additives and is already leaner (from my understanding - someone correct me if i am wrong here). perhaps changing out the main jet will give you the boost you are looking for... i wouldnt imagine you would have to do anything with the pilot jet, unless you are having a hard time keeping it idling, then you might want to check those too...

hope this helps, im not much of a mechanic, but i feel your pain when it comes to trying to sort out all of the annoyances that these tx/xs bikes can throw at you.

keep an eye on the cam chain tension.

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well on the head work i get a discount since i'm a mechanic and well i'm taking it to the machine shop we do busieness with. they said $75 for the whole job.

i hope there are no change in the pistons cause i put new ones on the rods already with new rings. well i'm hopping the new one piece head is just made better and such. and it'll swap on with some form of ease.

and yeah i know the feeling of buying it to learn on and to fix. so far i haven't broken anything myself. the last owners did all the breaking for me. i'm learning this bike rather run like poop than to run good.

i have to pull the carbs a part to fix one of them. right now i wish i could get both carbs to work at the same time. i don't know if jets are available for these bikes anymore. and i'll see what the thing runs like after i try to sync the carbs. which i'm hopping is another reason it runs bad. i know the new gas doesn't help me much either.

well thank you guys for the help so far. i'm going to bed here before i fall a sleep infrom of the computer.

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ive seen replacement jet kits for these carbs... total rebuild sets on ebay mostly... someone recommended one to me once, but i cant remember the name

it starts with a K though. kimuni? kuni? dont remember the name.

keep me up to date on how it all works out for you - good luck.

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ive seen replacement jet kits for these carbs... total rebuild sets on ebay mostly... someone recommended one to me once, but i cant remember the name

it starts with a K though. kimuni? kuni? dont remember the name.

keep me up to date on how it all works out for you - good luck.

cirrus based in canada do keyster kits and bits

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cirrus based in canada do keyster kits and bits

i'll have to look into those kits. i've bought 4 kits off ebay already(2 kits per carb). but if i need jets it's nice to know a place that sells them. does that company have a website?

well for a update not much has gotten done. still waiting for the parts i bought on ebay to be shippend and/or arrive. i'll speak up once thing start to move along.

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i'll have to look into those kits. i've bought 4 kits off ebay already(2 kits per carb). but if i need jets it's nice to know a place that sells them. does that company have a website?

well for a update not much has gotten done. still waiting for the parts i bought on ebay to be shippend and/or arrive. i'll speak up once thing start to move along.

http://www.siriusconinc.com/

http://www.mikuni.com/fs-tuning_guide.html

http://www.cameron-site.co.uk/nrp/

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thank you for the links there! i added them to my favorites.

well update! got the head yesterday! i see no cracks and it's pretty clean to me. so maybe next pay check i'll drop it off at the machine shop and have a valve job done and have it resurfaced so i know i have a flat gasket surface.

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howdy howdy.

well i mocked up the carbs on the 1977 head. they fit just fine. the shape of the 1974 and 1977 intake ports are a tad different. but not by much(openning wise). so i think maybe monday i'll drop the head off. and get the ball rolling on this thing and get it done. other thing on my list are fixing the carbs(one got plugged up and getting the float level right) and some wiring stuff.

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It will be interesting to see how this works out-hopefully in your favor. I have the same bike and may have to go down the same road you are. Mine has not run for 15 years. Keep the valuable info coming.

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Sorry to tack this on an old thread, but I am a little desperate.

Does anyone know how to properly adjust the cam chain tensioner on a '77 xs500? I have a shop manual coming in a few weeks, but if anyone knows, it would be greatly appreciated!

Thanks

Gregor

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howdy howdy.

well i mocked up the carbs on the 1977 head. they fit just fine. the shape of the 1974 and 1977 intake ports are a tad different. but not by much(openning wise). so i think maybe monday i'll drop the head off. and get the ball rolling on this thing and get it done. other thing on my list are fixing the carbs(one got plugged up and getting the float level right) and some wiring stuff.

I know I am really late on this post, but it definitely sounds like the needle and seat on your carb for the bogged down feeling when you crank it wide open. How did you make out with the bike thus far?

I am currently rebuilding one. So far engine looks in great shape and just rebuilt the carbs. However bike is in pieces as we speak. eek.

Ted

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Help,

It's difficult to find other folks working on tx/xs 500 . . . .

I'm at my wits end (not a long trip my wife will tell you). . . I recently took the heads and cylinders off my 1973 TX500 to get some work done.

I've reassembled everything, I've been trying to close/link the cam chain, but I can't get enough slack in the chain to get in the master link. Is there something I'm missing? I loosened the cam chain adjuster nut, and pushed the adjuster as far down as it will go (at least as far as I can push it) and then retightened the nut to hold it. I'm still about 2-3mm too short. Is there a procedure to ensure I haven't kinked the chain around the crank sprocket? I've pulled it, and rotated it backwards and forwards as far as I dare.

On a different note . . . the gentleman who bored the cylinder and checked the heads told me that the exhaust valve guides do not require valve guide seals. But, the parts guide/catalog shows that the engine requires 8 valve guide seals. . . . It really doesn't make sense to me that the exhaust valves wouldn't requires seals, but this bike is new to me, and I've never been inside one of these engines. What do you think?

Any help or ideas would be much appreciated.

Alex

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I'm having issues with my 1974 tx500 as well, yesterday i was riding and as i was slowing down my shifting to 2nd and 1st my bike started stalling and smoke came out the left side of engine .  I just got the carbs tuned and oil filter replaced and new plugs, but my bike seems to rev at high RPM's when i apply the clutch and hangs there when I'm in 4th or 5th gear, and the left carb is leaking from that spot in the image but like i said the left carb, any help would be appreicated,

carbs.JPG

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Really really really old post mate. 

 

I suggest you start a new thread

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air leak in butterfly spigot, not sure you can get them for that carb but try Mikexs in USA.

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