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79 XT500 How does it sound?

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I adjusted the valves and cam tensioner on my new to me XT. Second time around I pulled the decomp cable and polished the pits off the valve adjusters so it's as good as it's going to get. It sometimes wet sumps and I'm pretty sure the intake valve seal needs to be replaced. I'm debating if I should pull the top end, do the head and at least put in a new set of rings if the bore is OK especially since I really want to repaint the top end. Compression is 130-135 and I got tired of trying to kick the old gal over after I put some oil in the cylinder so I think the rings are good. Comments?

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My XT sounded similar before rebuilding. I think they will run a long time like that, they are a bit noisy on the top end anyway. I decided to rebuild since I am racing my bike. I sent it to a local flattrack guy to do the work since I wanted the bottom end freshened up as well. If I recall correctly, the top end "bearing" on the rod was worn and the timing chain was stretched. I had him replace both. I had valves, seals, and cam replaced as well, so no telling what actually reduced the top end noise. I forget what the guidance is about the visible threads on the adjuster and when to replace the chain.

Don't worry about the wet sumping, happens to all old XT's. It's not a big issue. Replacing the oil pump seals and the check valve fixed it on my bike.

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Thanks. I rode her for about 15 miles the other day. She's runs well but is a bit ticky. I'll plan on pulling the top end and repainting it while I'm having the header, kickstand and foot pegs blasted and recoated. I'll service the head and check the cylinder, cam chain and tensioner while I'm at it.

I couldn't hear any leaks other than a little past the rings when I pumped 100psi into her through my home made leak tester. And this was cold with no oil.

She doesn't smoke too bad after changing the oil a few times but I'll change the valve seals, check valve and pump seals since it's easy and cheap to do.

Edited by Sandstone

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They tend to be clattery. Sort of like an old Brit bike. One of the known problems is oil starvation to the exhaust lobe. Thumper Stuff used to sell the extra oil line kit to resolve that. be sure not to run too thick oil in it, Motorcycle 10w-40 Mobil1 worked fine. I gave myself problems using 20w-50: passages are a bit small and pump is only 12 PSI, so thick oil doesn't help at all.

I forget where the check valve is, but if you have it down for a bit, I'd soak the bottom end in mineral spirits, and pull the strainer at the bottom of the front downtube and clean it as well. If the cases soak in spirits when you have the top end off, drain it a few days before you plan to refill with oil. And then change the oil again soon after running. I mention this as mine had all sorts of goo in it from previous owners/sitting/etc. Finally, I ended up pulling the entire engine apart, it was amazing what crud was still in the crankcase. Mine was obviously a bad example. But usually, a good two-three day soak with mineral spirits will get most of it out. After it soaks, pull item #17 which is sort of a sump cover.

http://www.yamaha-motor.com/partviewer/?ls=sport#/Yamaha/XT500F_-_1979/OIL_PUMP_-_OIL_CLEANER/XT500F_(1979_MOTORCYCLE)/OIL_PUMP_-_OIL_CLEANER_(XT500F_-_1979)

You would want to do an oil change and filter after 200-300 miles after engine work anyway: gets anything that may have come loose or got in there, plus anything from new parts breaking in. They'll run and run in really bad shape, but are a hoot with a fresh engine, 38mm carb, free flowing exhaust, and big cam. Overbuilt, tough engines.

Good luck.

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Yamaguy55, great suggestion. I forgot about the dual oil line feed update. I did that too before rebuilding. It didn't change the clatter, but it's a very good fix to an original design oversight.

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Thanks for the comments. I've changed the oil twice with some cheap SuperTech 20W-50. She cleaned up a lot after the second change. When I got her the oil looked like it just came out of the ground and she was 1qt low. The tube filter had about 1/2" of dirt and sludge on the bottom and it took about 3 gallons of gas and some bits of rag shoved down the front tube to get it clean. Sump and sump screen were pretty clean. Anyone else having good success with M1?

I have a bunch of small parts coming in today including all the wet sumping fix parts. I love the fact that ~90% of OEM parts are still available from Yamaha but I'm looking for #15 (583-14431-00-00 SILENCER, INTAKE 1) in this diagram:

http://www.stadiumyamaha.com/pages/OemParts?aribrand=YAM#/Yamaha/XT500F_-_1979/INTAKE/XT500F_(1979_MOTORCYCLE)/INTAKE_(XT500F_-_1979)

I'll probably get the single oil line to the exhaust rocker upgrade from Mark.

I disconnected everything last night...boy those carb bolts have poor access, especially the right one. Engine is ready to pull today and today is a holiday :bonk: so I can hopefully have a look-see at the top end.

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Engine is out with rocker cover off. Intake valve stem is pitted and dished. Exhaust is dished I can't get the cam sprocket nut loose. Tried holding flyweel nut and also putting it in gear and holdiing the drive sprocket nut. Now both nuts are loose. Cam nut isn't left hand thread is it?

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I got it off by holding the hex portion of the shaft. Will post internal pics after I pull the cylinder.

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I've got a Dick Mann mk4 TT

It came with a recent dual feed line but I put the old line back on; it was direct to the exhaust. Aussie tuners have said that they still get occasional oil starvation problems with the dual lin but not with the single to exhaust mod. Since My engine is a first year TT with the 3 bolt pump I figure I'd rather not have the pressure halved. Protec cams used to come with the warning to switch to the exhaust rocker feed. They gave figures showing the feed to the inlet was still enough. All it does is reverse the flow path and feed the hottest part first. I think standard SR400s now come built the same.

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I'll have to find a hosting site to post pics but other than the pounded stem tips everything looked good and the engine is very clean inside. Cylinder looks good. The only weird thing I found after pulling the clutch cover was that the cover gasket was leaking into the engine at the bottom of the oil filter cavity next to the check valve. The check valve was good so now I know where my touch of wet sumping was coming from. The cam measured up fine. I'm dropping off the top end at a local machine shop either today or next week to have them clean it, measure it up and we'll go from there.

Has anyone had success in grinding the valve stem tips flat???

On the oil line...the single exhaust line or the balanced Kedo classic instead of the race twin feed line is the way to go.

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Don't forget to check on the small cushion washer is in place on the cam cam tension plunger.Without it,it will sound horrible.

Did THAT once years ago...A new rebuild sounded worse than the old motor..#19

http://www.yamaha-motor.com/partviewer/?ls=sport#/Yamaha/SR500E_-_1978/CAMSHAFT_-_CHAIN_TENSIONER/SR500E_(1978_MOTORCYCLE)/CAMSHAFT_-_CHAIN_TENSIONER_(SR500E_-_1978)

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The tensioner washer is there but I have a few other questions:

1) I'm not sure how to check if the cam chain is OK. The Haynes manual is vague on the subject and the factory manual has nothing about inspecting the chain.

2) I also found this oil line to the exhaust which supposedly can off a TT:

http://cgi.ebay.com/ws/eBayISAPI.dll?VISuperSize&item=390068668467

I've never seen this style before. Is it one of the aftermarket oil lines, a homemade one or is it mislabeled and from another bike? I'm not sure what that bracket would attach to.

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I have everything back from the shop. I used Micron Engines in Stone Park, IL 708-343-6007. Mike there was very helpful in answering my questions. He did a great job faster than expected and at a fair price. It was nice to have the head and cylinder done at the same place that was only a short drive away. Everything checked out OK so Mike cleaned/bead blasted, recut the valves, replaced the springs and seals, took about 5 thou off the stem tips and honed the cylinder.

The cylinder measures 3.4260 -3.4265 in. with the piston at 3.4225 - 3.4230 in. so let's call it a 0.003 piston to bore clearance. The factory manual which I now have says the piston to bore clearance should be 0.002 - 0.0022". Is 0.003 - 0.004 a problem such that I should pick up a new piston or bore and oversize? I was hoping to just replace the rings. Anyone know what the stock STD piston diameter spec is since the manual says 87.00mm and I know that's not possible when the bore can be the same size.

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Found out that the 945 on top of my piston and the -002 on my barrel mean that the piston originally was 86.945mm and the barrel originally was 86.998 which put the original clearance at 0.053mm which has grown to about 0.10mm. New parts on order for a bore to 1st OS.

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