1984 XT600 Yamaha Dual Sport Bike Rebuild
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09/14/04 - The bike has been running fine. Had a couple 5 mile rides nearby. With the new factory clutch lever and perch, the clutch disengages far better and I can find neutral more often. I also ordered and received factory mirrors, so now the bike is legal. Ordered and installed some gasket material for the tail light too. Gave rides in the driveway to Leah and Toni. A very nice feeling having a cute woman on the back! The bike's size makes it easy to take 2 people. The only major work left is the oil leak on the right side of the motor. I think that's the only location leaking, but it leaks like a seive. It will be more obvious after I replace the gasket. The oil and filter will also get changed as well. Hoping to get the missing reflectors for the front forks and the tool kit to fill in above the tail light. Looking forward to truing and balancing the tires. The rear one is so bad it shows the heavy side down while still on the bike! I think I will take off the 48 tooth rear sprocket and put on the new 42 tooth one for better overall driving. First gear is a bit too low right now. Can't wait to take the driving test so I can get M1 motorcycle endorsement on my license. Since I just had surgery, I'm not ready to terrorize the streets just yet anyway. But when I do....!
09/04/04 - While at DMV I found out I had to take the automotive test as well as the motorcycle test. What a stresser! Only missed one question on the auto test. Flunked twice on the bike test, but passed on the third try only missing one. Whew!! Now I have a motorcycle permit which does not allow riding on freeways, at night, or with a passenger. Took a few rides around the hills in this part of San Jose. Lotsa fun. This thing is still hard to start, but runs well. The new carb clamps didn't change the way it runs, but at least I know it's assembled correctly. Just made a new order for mirrors and the clutch lever assy. I prefer a restoration approach. The mirrors will make it 100% street legal. The air shocks have held their 12psi of pressure without leaking. I am happy about that. Although rebuilding the forks would be good experience. Still need to get the proper armor apparel in case I dump it. There is a large motorcycle riding park not far away south of San Jose. I can't wait to explore it. They have trails rated like ski slopes. The bike starts to vibrate a bit at around 35mph. I know the rear tire is out of balance as well as both tires being out of true. I have a spoke wrench and am looking forward to trying my hand at tire truing. I have an industrial high point balancer that will allow the tires to be balanced once they are trued. The motor has a bit of clattering as the rpm's are increased. Don't know if it's piston slap, pin slap or what. Doesn't sound like the clicking of misadjusted valves as I have been through that already. Listening too another XT600 would be very helpful. It's also about time to change the oil. I will do that when I replace the leaking right side engine case gasket.
08/20/04 - The bike sounds like it needs a valve adjusted. Carb clamps are on order. They should help with the rough running and starting. It really is hard to start. Several rubber grommets and other misc parts are on their way. The headlight comes on and then dies out. I'll have to look into that. The trans shifts very nicely but the shifter is a bit stiff. Hurts the top of my foot. Don't even need the clutch. The clutch drags a bit. The engine leaks oil a bit. So far I'm very happy with the carbs. Sometimes I forget to shut off the fuel and they don't flood the engine. Getting the title is under way. I handed everything over to Don's Lein Service. He takes everything to a DMV for professionals, and will hopefully be able to get the title and registration ready in a couple days without too much cost. In the mean time I'll go down to DMV and get the written test out of the way. I hear it's only 10 questions. After the registration is ready, I'll go take the driving test.
08/17/04 - The timing chain guides and many other parts arrived today. They were used but in great shape. So I buttoned up the rest of the motor. The magneto went on with a new woodruf key. The timing chain adjuster only went in about 6 clicks. That's less than half of what it was before. Both side covers were installed. I messed up the gasket on the right engine cover. Dripped oil like a seive. I pulled it apart and realigned it. We'll see if it still leaks tomorrow. While it was draining there was a lot of fine aluminum particles in the oil. Hopfully this was some left over from when the timing chain ground away the inside of the case. The engine would only run if it was primed with fuel directly into the carb. After a few tries and with the choke on it holds an idle ok. The carbs need clamps so they seal to the engine better. I forgot to put the vent tube onto the top of the valve cover. It spewed oil all over the motor. I sprayed carb cleaner over the engine to evaporate the oil. Eat me tree huggers! The motor with the gasket realigned seems to not leak oil now. Glad to see that there is oil pressure! The mounting bolts all need to be tightened and some odds and ends bolted on to make it complete. Tomorrow I should actually get to ride it and test the transmission. I actually bought motorcycle oil so that the clutch will work its best.
08/02/04 - Since the cam sprocket arrived today, I put in the timing chain and cam gear. The only holdup is that the motor needs good timing chain guides. They haven't been shipped yet. Sigh. Lots of misc Yamaha factory parts came in. That will help with assembly once the motor is done. I also picked up a XT350 parts bike for $150 yesterday. It didn't have a front end. None of the plastics or rear fender fit the XT600 except for the headlight cowling. Dang! They are nice too. So they all went on Ebay. At least it came with the turn signals and headlight frame that do fit. If the electronics are good it will be nice to have spares. The extra front wheel is very heavy duty and in good shape. The rear wheel is a bit dented, but it's tire is very nice. When the next batch of parts arrive it will be time to get it running!
07/30/04 - I chased down a local vendor and bought a new timing chain today. It's sold by K & L in Santa Clara thru Road Rider on Monterey Road in San Jose. As it turns out the chain can't go in because the cam gear has some minor gouges in it. The good used cam gear that I bought off Ebay should arrive Monday. Also the parts from BikeBandit.com are due Monday. With the cam gear and new chain in hand they should drop in nicely. When the timing chain guides get here later in the week, then the motor will be ready for starting.
07/25/04 - I measured the length of the clutch springs with calipers. They were at factory spec. So were the clutch disks. Flatness was excellent as well. After looking at clutch posts at Thumpertalk.com, it was pretty clear that clutches are a pain for everyone sometime. One of the tips was to remove the glaze from the disks with 320 Wet or Dry sandpaper with oil. I did just that and cleaned them with carb cleaner afterwards. I reassembled the clutch bone dry. Disengaging the clutch allowed the back wheel to spin freely without spinning the motor. This was good news. Then I took them apart again and coated them with Dextron trans fluid and reassembled the clutch. The clutch dragged a little but still allowed the wheel to turn without moving the engine past the compression stroke. This is vast improvement over no disengagement at all!! Now all I need is a good timing chain to test the motor! I bought a bunch of parts that include a used timing chain and guides. I should buy new stuff, but if used parts save me money it might be worth it. Although now a new chain would save me a week in lost time waiting for it. Hmmm.
07/24/04 - Great news. The stripped crankshaft threads were salvagable because it appears the nut lost much more of it's threads than the crank did. Running a 14mm die carefully over the threads took out the nut's thread remnants and generally left good crank threads. So a new flange nut needs to be ordered from Yamaha. This was a great relief that the crank is still useable. Next I pulled the timing chain guides out and they need to be replaced. The rear one had some damage and the base is bent slightly. The front one is almost cracked clear through. With better or new timing components, that should fix the timing issue. Once again I looked over the clutch plates and can't see anything wrong with them to cause the clutch to drag so bad. I wonder if wet clutches are suppose to drag alot. But then how can a bike be bump started if this is the case?
07/23/04 - Today was a momentous occassion. The crankshaft has the threads stripped that hold the magneto on. The fellow on Ebay that sold me this clutch cage removing tool (Ebay item #2485206635), also recommended that I use a Craftsman strap wrench for holding the magneto while trying to get the nut off of the stripped crankshaft. The amount of force that it took to remove the nut was incredible. With a 24" breaker bar and the strap wrench I gave it all I had. On the second try it finally broke loose. The nut was stripped as well as the crankshaft. Not unexpected. Then I took an old harmonic balance puller and removed the magneto. I had to go to Mr Metric to get the very long 8mm x 130mm bolts to reach into the magneto. Three tries and a couple of hammer taps and it came off!! I never thought it would. I also got a 14mm die to help try and clean up the crank threads. I was thinking about going to smaller diameter threads, but I think there is enough thread to hold the nut tight. The goal today was to see how loose the timing chain was. Since it's located behind the magneto, the mag had to come off. The chain at full adjustment is very loose. No wonder it skipped teeth. So at least a new chain is needed. The timing gears look ok, but I have not decided weather to replace them or not. Although I did order a good used one off of Ebay as well.
07/20/04 - The carbs are holding fuel nicely. What a sight! But right now the bike won't start. Even with priming thru the carb and
thru the spark plug hole. The thing that I think may be contributing
is that when I am checking the cam timing, if the crank is turned
backwards, the lower timing gear slips a couple teeth and knocks the
cam timing way out of whack. I'll reset it again and do a compression
check to see if the valves got damaged again or not. Should turning it
backwards cause it to skip a few teeth? The chain tensioner for the timing chain is at it's max. This means
that either the chain is stretched or the chain guides are badly worn, or both. To top it off the
flywheel/magneto end of the crank, has stripped threads all the way up
to the nut. This was damaged before I got the bike. I don't dare try
and take the nut off for fear of never getting it back on. Ironically
if I found a decent price on a chain and guides I would have to take
off the nut/flywheel to replace the chain. Sigh. The timing chain also looks like it does not engage the cam gear teeth
very deeply. As the chain bends to go around the teeth, the chain
seems to sit a bit high on the teeth. I wonder if this is normal?
07/18/04 - The 2nd order of valve guides arrived. Ordered 2 just in case one gets messed up again. Fortunately the first valve guide installed just fine this time. The guide was put into the freezer to help reduce it's outside diameter. Instead of pounding in the guide this time, I made a fixture to pull the guide through using a 4.5" and 5.0" long 1/4-20 bolts. Heat shrink tubing was added to the bolts threads to protect the guide's inside diameter from damage. The other aluminum part was turned on the lathe to fit the valve seat exactly. The way it ended up working was to tighten the nut, then tap the head of the bolt with the ratchet. You can see I dinged the aluminum gasket surface with the ratchet. Turns out a hammer worked better. The hammer would allow a 90 degree rotation of the nut before getting too tight. Then the head had to be tapped again. Trying for more than 90 degrees resulted in a snapped off bolt. This tap and turn method took longer but was much more gentle on the valve guide. I only had to debur the very top of the guide to allow the valve to pass through after it was installed. The guide stopped going in easy, so I reheated the head and guide in the pot of boiling water again. That helped finish the install. As it turns out the valve seat in the head was still aligned with the valve's face, so I didn't have to have the seat re-cut. The guide didn't need reaming either, even though I bought a 7mm reamer just in case.
07/16/04 - The guys on the XT/TT Yahoo group convinced me to use a standard oring with lithium grease to hold it in place during assembly. It worked great. The fuel bowl does not leak any fuel at all now!! During the draining of the fuel bowl small particles of grease were observed. So I ended up draining the fuel bowl 3 times. Makes me wonder if vaseline would work better, as I think it disolves in gasoline. So the carbs are fully assembled now and ready to run. This also means I can put together a carb "renew" kit with all of the orings I've fit to the carb. I'm thinking $10 per kit. Since nobody on the planet suppies carb kits for the XT600, it's a bargain. The new valve guides should be here today or tomorrow to allow for another experiment filled weekend!! Getting the head done finishes the engine. Sometimes a new guide requires re-cutting of the valve seat in the head as well as reaming of the guide with a 7mm reamer. We'll see how lucky I get!! The front and rear fenders came in today. They are used original Yamaha XT parts. Glad to have them.
07/13/04 - I bought a 10 qt stainless bowl from Target to heat up the head to help remove the guide. So if it gets trashed there is no real loss, just $6. It barely fits the head. The water level is about 3/4" from covering it. It boiled after maybe 15 minutes or so on high. Proves that water and oil do mix if you boil it. Grabbed the head with leather gloves, ran onto the balcony and hammered out the old guide in about 4-5 hits. Lined up the new guide and started pounding it in with the drift I turned from a 6061 aluminum rod. The 7mm diameter tip of the rod that fits into the guide would bend a tad if I did not hit it perfectly. The drift handle was 1/2" diamter. It started slowly sliding into the head, but I kept bending the tip of the drift. This was the downfall. With uneven shock load to the top of the guide it finally cracked and a couple small pieces fell off. So I had to admit defeat, reboil the head and pound out the new damaged guide. I had forgotten to put the guide in the freezer as well. Sigh.... Here it is being boiled to remove the new guide. guide2, guide3. Time to order more guides.
07/05/04 - Here are the valves seated in the head. It's easy to see the marks on the valves where they hit the piston. They were bent, thus causing almost no compression. My automotive valve spring compressor was a bit large to fit the tiny valves, so I machined an old 19mm socket into a tool to help it fit the springs. I eventually figured out how to straighten the bent valve heads. By placing the valve stem in the mill, then coating the flat side of the valve with a wipe board marker. The aluminum tool in the vice acted as a high point indicator. The head of the valve will scrape the aluminum indicator, removing a bit of the marker to show where the high spot was. Then I would just move the table over to place the edge of the vice under the valve. By bringing the knee up and measuring the distance that the valve was bent back, I could keep track of how much distance the valve was being bent. A few cylces of this process turned out nicely straightened valve heads. The one valve that had a bent stem was straightened using a technique I use for straightening helicopter shafts. Next I had to try and recut the 45 degree valve faces. Using the mill made chatter marks on the face. So the lathe was set up to cut new faces at a 45 degree angle. This worked great! It left a very nice shiney face on each valve. The red die on the valve is used to see if the valve face touches evenly around the valve seat in the head. Then the seats were lapped to the valves with grinding compound. Using a cordless drill to slowly spin the valves in the head, made fast and clean work of the lapping process. So now that the valves have been saved (Yippeee!), the busted guide will get replaced when it arrives. I think the motor would run fine with the valve stem seal being gone on the broken guide, but the way the oil flow is layed out, the oil will pool around the exhaust valve and possibly cause the motor to smoke. Here is a shot of the valves after the lathe operation and after being tested to fit the valve seats. Notice that the red die is missing on the top 2/3 of the face. That's exactly where you want the seats to hit. The entire cause of the bent valves were that the timing chain somehow was not in time or came loose. It also ground away some of the sides of the case. This could explain the aluminum powder in the oil. The case is still useable.
07/03/04 - The motor is now out of the bike. A couple of jackstands held the frame upright as the motor was dropped out with the new lift. There seems to be some oil starvation damage. The cam and it's bearings in the head show severe scoring. There is some severe damage to the left end of the crankshaft that holds the rotor. Someone stripped the nut on or off or both! The piston has valve notches that don't look exactly factory. I remember thinking what a wimp I was for not being able to kick the motor over. Although even the Yamaha factory manual shows two notches in the piston. The rings looked ok and the scoring was not bad on the piston's skirt. The top of the piston had been cleaned by someone as there were sanding marks on it. The bottom side of the piston was still very clean. The cylinder bore was nice. It had some very shallow angle honing marks. I suspect this was from a home brewed attempt at refinishing the cylinder. The front chain sprocket slid in and out on it's splined shaft about 1/4 inch. Hopefully there is just a spacer missing. Here is the motor disassembled. The clutch and transmission still need to be taken apart and inspected. A view of the frame shows that the motor is actually a structural member of the bike frame.
07/01/04 - I picked this XT600 up on Sunday 6/27/04 as a basket case with no title and a bill of sale written on the back of a Marlboro carton. It kicks over but won't start. Fresh gas didn't help. There is a spark. The carbs leaked fuel badly onto the cranks case. So I removed them, cleaned them, and am waiting for parts. I hope I can get the carb parts for this 20 year old machine. Internally they are in great shape although the bowl gasket is bad. The bike is missing the side panels, headlight, tail light, both rear fender parts and one front air scoop. The guages have some damage. The tank is whole but has a knee dent on the right side. The front forks have shrader valves for adding air pressure. I don't think that is stock. The front suspension feels real soft. The front brake is very weak. I tried to revive the master cylinder and bleed the system on 6/30/04 but it didn't help. It needs a fresh rebuild kit. But at least I got the frozen rusty screws out with my mill. The clutch lever is not pointing in the right direction, maybe that's related to why the clutch won't disengage. The head to frame supports are missing. I also picked up a motorcyle lift from Kragen per Brad's recommendation. They have two styles. One is red, one is black. The black one that I got on 7/1/04 raises the bike to 16.5". The red one is shorter, 16lbs lighter, and lifts to 14.5". They are on sale over the 4th of July weekend for $50 at Kragen Auto. A compression test on 7/1/04 shows a whopping 20 psi!! Time for an engine teardown.
Brad's '86 XT600 Project
For any questions please email me at mikep_95133 at yahoo.com