ramblerdrver

Haver you checked with Speed & Sport Yamaha for carb kits? They have a website and seem to have lots of parts for old Yamahas.

I've had a couple xs400's and don't recall the valves being that noisey(but, then, I sometimes forget what I've gone out to the garage for!), altho, as mentioned above, the microphone may accentuate the noise. I forgot how the valves are opened...thru a rocker arm from the cam in the head? Could the rocker arms &/or shfts be worn? You might try using a stethoscope (long screwdriver works!) or length of hose to listen to various areas around the engine to be sure noise is coming from the valves

I tried a while ago to get into the Yamaha Club home page and what showed up was an installation page for something called "Joomla!"!!!! What is it? Is it some kind of spam or virus that someone has attached to the site?

Changing oil shouldn't make the valves noisier...assuming, of course, you've got enough oil in the crankcase! Adjusting valves is a bit tricky...kinda a pain in the rear, actually! There's suppose to be a "slight drag" on the feeler gauge when clearance is correct...but just how much is a "slight drag"??!! If the feeler gauge is pulled at a slight angle, it'll affect the drag! And tightening the lock nut may change the clearance! Might help to have three gauges...one at minimum clearance, one at max, and one at median clearance (there's usually a range of settings...like .004-.006). These will act as a go/no go check. You can make your own "angle feeler gauges"...just bend the straight ones!

I previously posted this: "Speed & Sport Yamaha shows "aftermarket" filters availiable for about $16 plus shipping. I ordered one for my newly aquired 1974 TX500, using part# 371-13440-09-00. What arrived was one that says "replaces Yamaha 371-13441-90". " Well, I've now used the one I bought and it works fine! There's very little room to get the filter into place on these bikes, so a slightly shorter one works well. I previousily got a set of 3 filters from a fellow on eBay which were suppose to fit...but they didn't, even tho they looked almost identical to the original I removed from the bike. The difference was in the shape of the top of the filter...the original was slightly angled off, these from eBay were square and couldn't be fit into the place behind the left side cover (the cover covering the generator and starter and balance chains)without removing the cover...which you don't want to do just to change the filter!. So beware!

Here's a link to the Yamaha Parts catalog on the web: http://www.yamaha-motor.com/sport/parts/home.aspx You can compare parts there between years and models. The carbs on a 74 TX500 look to be same as the 1975 XS500. But the 1976 carbs appear different...the 74 & 75 venturie slides are activated by pistons, while the 76 has rubber diaphrams. They might still be exchangable (as a pair). These carbs (from all years of the XS & TX500) are attached to a common plate with screws and then the plate is clamped to the head thru a short rubber coupling. Not sure what other motorcycles used this method, so finding other carbs to use from other makes and/or models may be hard to do. CORRECTION!...the carbs on the 1976 XS500 (and 77 & 78 probably) DO NOT first mount to a plate... they clamp to the head directly thru a rubber manifold, like many other motorcycles.

Well...to begin with you will need a repair manual...if the one you have is a Yamaha factory manual, good! If not, get one...they can be found on eBay in CD or "paper" form. You also should get a book on repairing/restoring "old" motorcyles, which should give lots of helpful advice. I can't give a specfic title or source for such a book, but am sure they are out there. Also, look over the Yamaha website...they have a parts section where you can find the parts breakdown for your bike, which will be good for determining what goes where and what the part numbers are. parts are a bit hard to find for these, but sources include Yamaha (probably mostly parts that are common to more popular models), eBay and places that specialize in new and used parts for old Yamahas, like Speed & Sport Yamaha. As far as whether to start by tearing it all down and fixing what you find wrong, or try to get it running first...guess that depends on how complete it is to begin with and how much of it is still hooked up. Sounds like you are looking forward to this as a learning project, so starting with a complete disassembly is a viable way to go. However, disasembling (and reassembling!) a complicated motorcycle engine can be intimidating at best and something you might want to avoid if the engine is basically sound to begin with. So you might want to try doing some initial work to try and get it running, to listen for any unwanted noises and see how well it runs and shifts. If you decide to try to get it to run, a few things you need to do or check. First, change the old oil (and filter if possible...they are hard to find...but Speed and Sport Yamaha has them)...and let the old stuff drain out overnite to be sure all the old "crud" has a chance to drain out. Remove the spark plugs and squirt a couple good squirts of oil into each cylinder to oil up the rings and cylinder walls. Now, with clean oil and some oil in cylinders and plugs still out, kick the motor over a few times. This will help prime the oil pump to start oil flowing to the filter and bearings. Put the plugs back in and give it a kick or two to check that it has noticeable compression in both cylinders. If not, it may be a sign to go ahead and start disassembly! If there is compression in both cylinders, take a look into the gas tank...is it clean or filled with foul old gas and/or rust? If so, that will need cleaned out so the new gas doesn't wash any of the crud into the carbs (assuming the fuel shutoffs aren't plugged with rust and old dried fuel!). To just get the motor going you might be able to rig up a separate tank temporarily to supply fuel to the carbs. If bike was put away when last used with fuel still in the carbs, they will most likely need cleaning before the motor will start. Also, the points will likely have corroded over the years and they will need cleaned and adjusted. When everything is "right" the motor should start and run fairly easily (it may take some work, however, to get to the point where "everything is right"!). It should also run fairly quietly (for an aircooled motor) and smoothly, with no knocking, banging, rattling, etc. My TX500 (1974) set for at least 2 years without running before I got it. It now starts easily and runs fine, but to get it there required cleaning the carbs, new spark plugs, and cleaning the points and setting them correctly. If needed, take lots of photos along the way to help you remember how it things go together! Good luck and always try to remember "this is fun!"! :-)

I tried insuring my 1974 TX500 with Progressive thru local agent and they a TX500 wasn't listed...but a XT500 was (for 1974)! I figured there was a typo error in Progressive's information, so let it be insured as a XT500. The insurance covers liability mostly, not the value of the bike.

The specs for the intakes were listed: .006-.008". If the chain seems tight at the top it's probably fine. The manual says if you loosen the tensioner nut you should hear it "snap" the chain in place...so I assume if you hear nothing then the chain is already tensioned correctly. There are some sprockets and some "rubbing blocks" in the assembly that I suppose could be worn and causing trouble. Maybe try turning over the motor by hand and watching the chain to see if all the rollars are there and there's no obvious worn spots on the chain. I think to investigate further you'd need to remove the motor from the bike and do more major disassembly.

Clearance specs are .006-.008" for intakes, .008-.009" for exhausts. Adjust them at TDC on power stroke, using the TDC ignition timing marks in the breaker point housing. Adjustment is with a screw and locknut. The noise could also be a loose timing chain. When you have the valve cover off you can see if the chain is loose. There's an "acorn" nut located near the cylinder/crankcase joint at the right front corner. If you loosen this nut the cam chain tensioner should "snap" against the loose chain and tighten it back up. Then tighten the nut back up. If it doesn't tighten up, something is worn...chain or rubbing blocks. You should get a factory service manual for this bike. They are availible on eBay in CD form or paper. They aren't the greatest manual ever written but are much more informative then a few lines of infor here. And they have pictures!

Main body gasket...the "paper" gasket on the backside? Make sure all old gasket has been removed and that the backing plate hasn't gotten bent and that the screws aren't bottoming out (they have small lock washers, that, if missing, may allow screws to bottom out). Or do you mean the o-ring between the valve and tank. If that, be sure the o-ring has stayed in it's grrove AND that the attaching screws have fiber washers to seal them off to the valve body. Drain screw...there's a fiber washer there to seal it off to the valve boddy. Front off/on/res lever...it's kind of easy to not get this seated fully. Also, I think there is a front & back side to the rubber valve washer. The side that goes to the lever has a ridge around each hole, which acts as the sealing point. Gasket sealer...probably not a good idea, as it would need to be gasolene proof, not mearly gasolene resistant...and that might be hard to find.

Question about setting the timing on a 1974 TX500. The book (factory service manual on CD) says set static timing first, then set timing dynamically using a timing light. Timming is suppose to be 40 degrees advanced at 2000 rpm. The point cam plate has marks that supposedly corespond to the 40 deg. advance. But the 2000 rpm figure...is that cam rpm, not crank rpm??? The manual doesn't say. Mine needs to be rev'd to about 4000 engine rpm for the timing to hit the marks on the point cam plate. And the marks on the point cam plate (TDC & 40 deg advance) don't appear to be 40 degrees apart. ???? Thanks

The original size should have been a 4.00x18. My opinion is to stay with that size. Don't go with a newer size designation even if there's a cross reference saying they're the same. Seems to me that even with the same size designation , tires can vary in actual size between brands. IRC, among others I suppose, makes a "street" 4.00x18. The front tire should be a 3.25x19. I put a new IRC tire of that size on my 74 TX500 and there's only about an 1/8" clearance between side of tire and the main center fender support!

Thanks!

You can get a new gasket (the one behind the lever...if thats where the fuel is leaking thru) from Yamaha (#137-24523-00-00) or check on eBay or with Speed and Sport Yamaha. The other gasket & oring should also be availiable from the same sources. Perhaps there are 2 shutoff valves because the construction of the tank doesn't allow the fuel to easily flow from one side to the other.