XS400J Maxim 82/83 DOHC engine rebuild

DynaGlide

XS400 Enthusiast
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Let me start by saying I'm not an import guy. I've owned my Harley-Davidson Fat Bob since new in 2009 and it has been my bike to learn how to wrench on. Over the winter I did a complete cases up engine build on it and that left me wanting to find a new project.
That being said, I've wanted to get into an older bike for a while now and through a series of circumstances I ended up with this Maxim engine to mess with. My friend is a big Yamaha guy and he had this sitting under a pile of stuff in the corner of his garage. He got the bike for $80 and basically told me have fun with the engine, see if you can get it running. Ultimately I think he/we will chop the bike up and turn it Cafe. I don't care about the "Harley" vs "Metric" attitudes some have, I enjoy all motorcycles mainly because I love learning how they work or were built.



On the outside the engine is in pretty terrible condition but as far as I can tell mostly together/okay. Just years of neglect and I suspect some faulty oil seals before being stored:


When I got the carbs apart I was surprised to see them almost perfect:




The cylinder head valve seals were definitely bad, some of the ports are pretty ugly inside I can take a pic later, but I got them disassembled:





One thing led to another, a bunch of dirt got into the crankcase taking the top end off and I went ahead and split the cases. (A word of caution to anyone following this for their own DOHC. .there's a case bolt hiding behind the oil pump which the manual doesn't tell you about. I found out the hard way):



I'm normally a lot more careful working on things but so far I've approached this thinking it would get parted out. The further I went I realized it looks pretty good inside I have a chance here. I'll be relying on the community for help as I clean this up and get it back together as the manual for the Seca available from this forum isn't that great and I can't find any threads on a DOHC engine so I'm starting one.

A small 3.5 gallon parts washer gets in today from Eastwood, should help out with all the messy stuff. Plenty of stripped bolts along the way need replacing and the stator is pretty much a goner. I'd like to clean up the engine but don't have the patience to polish it up and I'm on a budget, open to suggestions.

Wish me luck.
 
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Well the 3.5 gallon parts washer didn't pan out. It was from Eastwood and the pump was way too strong. Small tank + strong pump = big mess. I packed it up and sent it back. Instead I opted to take the cases to a local machine shop to let them hot tank them. I've tried cleaning really greasy/oily stuff at home in the past and I just don't have a good way to do it. If anyone has any tips here I'm all ears. What I run into is I end up with a tub full of gunk that I'd have to drive to the landfill 20min away, or I go through several cans of brakleen. Neither options appeals to me. On to some more pics:

The stator was so corroded I had to rent a 5lb slide hammer to remove it:





Gears out:





Starting to get organized:



All stripped and back from the machine shop:





Now I have to go and clean all the gasket surfaces and see about cleaning up the stator mounting area. Also had a starter bolt strip out in the threaded hole it mounts to. I believe it corroded to the aluminum housing. Might be taking that back to my new machinist friend to fix. As for the oxidized finish on the cases I haven't decided what to do there. Would like to clean them up but haven't found a shop local that messes with that sort of thing.
 
Hey Dyna, not a lot of complete engine rebuilds here on the forum so I'm excited to watch your progress! Things are looking really good... now that it's been cleaned inside. Man, that photo of the split cases was really nasty. Amazing how well the machinists cleaned that up.

Do you have access to a sandblaster? I recommend using a walnut medium to clean the corrosion from the outside of your case. Walnut is EXCELLENT at removing surface crap and won't change any dimensions. I walnut blasted my cylinder head and it removed all of the carbon, made it look brand new, and took all of 10 minutes. It will also remove stuck gasket material pretty nicely. Perhaps another option (if you want to paint the case) would be to plasti-dip all of the mating surfaces and hit it with a glass-bead blast. The plasti-dip will protect the mating surfaces from damage and the outside of the case will have all of the corrosion removed and be nicely prepped for a coat of paint. Best part of doing that would be no seals or parts = cure the paint in an oven.
 
Thanks for replying, was starting to wonder if anyone even cared I was doing this.
I've been trying to locate a blasting outfit without much luck. The only ones that do Walnut are for German cars, I get the feeling they would try to charge a lot for me to have it done, or wouldn't even bother. I'll keep looking though. I use plastidip on my bike but I have a hard time seeing how it would stand up to sand blasting?

I wish had a contact that would do these small parts for me. Maybe someone out of their garage. Back to Google.
 
Do you have an air compressor? If you do, a 50lb bag of ground walnut media and a siphon blasting nozzle are only $30 each, so for $60 you could easily blast all of your parts. You could probably recover a lot of the media too if you enclose your space properly.

My idea for the plastidip was that the sand or glass media will just bound off it, so if you cover mating surfaces (where you don't want any change in dimension like you'll get with the glass and sand) with a rubber coating then it would be easier to blast everything. Just a thought :) Kind of depends on you finding a blasting solution though. Have you heard of soda blasting? That could be a good alternative to a bigger sandblasting setup. Basically you do the same thing (siphon nozzle, homemade or purchased) and blast your stuff with compressed air that is siphoning regular old baking soda.

p.s. I have a soft spot for engine rebuilds. Sure a good build thread is a joy to scroll through, but nothing is as interesting or rewarding as watching/completing an engine rebuild especially when there are so many pictures! So yeah, people care but not everyone has rebuild experience.
 
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p.s. I have a soft spot for engine rebuilds. Sure a good build thread is a joy to scroll through, but nothing is as interesting or rewarding as watching/completing an engine rebuild especially when there are so many pictures! So yeah, people care but not everyone has rebuild experience.

Well you're in luck. I took some parts down to my Harley mechanic today. He has a real nice shop and is good about letting me use his equipment. Thanks again Chad.
I spent a couple hours walnut blasting. Here's some pics:














That walnut blasting is really cool. It just eats right through carbon and surface build up. It took a lot of white stuff off the engine fins. The base gaskets are so baked on that I'll have to use something to break them up before trying to scrape what's left off. The funny thing is i keep finding parts that might need replacing that were hiding under all the years of deterioration.
 
Ooooh yeah baby! It's like magic how well it can clean hard dirt and carbon. All that white powder was likely oxidation, and the base gasket can probably be removed if you hit it with some gasket remover, carefully scrape it a bit, then let it dry. I found that was enough to lift the really tough stuff so the walnut media could get a solid hit on it. Any plans to paint or are you keeping it bare?
 
Ooooh yeah baby! It's like magic how well it can clean hard dirt and carbon. All that white powder was likely oxidation, and the base gasket can probably be removed if you hit it with some gasket remover, carefully scrape it a bit, then let it dry. I found that was enough to lift the really tough stuff so the walnut media could get a solid hit on it. Any plans to paint or are you keeping it bare?

I think I might have to transition photo hosting services or start my own, some of the pictures aren't showing up for me now.

There's so many shop tools on my list of 'wants' and now a big air compressor/blasting booth are high on that list. No space or money for those any time soon. I think the plan is to paint the engine eventually I just wanted to get everything clean so I can focus on assembly. I'll pickup a stainless steel welding brush at Home Depot and see what it does to the cases with some elbow grease. Those orange o-rings at the cylinder spigots were completely hidden from sight until I started blasting away. Kind of fun to do but it did get old after the first hour at it.
 
I ordered gaskets yesterday off eBay. I'm not positive what all is included but it looks like the first set has the valve stem seals, cover gaskets, o-rings and the second set is a complete oil seal kit. Worked out to about $83 all in, definitely better than buying this stuff individually.

http://www.ebay.com/itm/151231608033 "MS Motorcycle Engine Complete Gasket Set YAMAHA XS 400 DOHC 82-84"

http://www.ebay.com/itm/160880828810 "KR Motorsimmeringe YAMAHA XS 400 DOHC R/J SECA ..... Engine oil seals OSL-212"

Once they get in I'll print off the parts diagrams and start matching things up to see what all I have and what I still need. That's going to take a while I think.
 
Looking good! I tried soda blasting and thought it was awesome. Compressor couldn't quite keep up though.
There's a diy blasting place in town that has walnut. Might give it a try next time. Good to see how well it works too.
 
Not much to report. The walnut blasting gummed up this bearing pretty bad, so I had to buy a blind hole puller to get it out. Local Advance doesn't carry one in their tool rental program.



Tool was tough to use in confined space, I ended up digging into the bore past the bearing that the shaft goes but I think it's just cosmetic. New bearing off eBay for $7 shipped on the way. I will heat the case and freeze the bearing and drop it in since there's a shoulder for it to rest against.
 
That's a lot of work so far, on a motor that may or may not be good, for a bike without a bike!

Looks like fun!

Ha well I'm way past the point of no return here so I'm going to give it my best to see this thing run. I try not to let myself get overwhelmed and take things one step at a time but there's been plenty of head scratching moments where I wonder if I bit off more than I can chew. Now that everything is clean and starting to go back together I'm feeling better about all this.

Starting to re-assemble now:

Oil baffle plate is back in along with the bearing rings with some assembly lube:



Through a lot of trial and error and looking at the manual I think I have the transmission back in:



It seems to shift properly. I took the gear sets out and tried things, put them back in, tried shifting until I was satisfied. The book tells you which order to do what and I think following that it's somewhat foolproof.

After I get the shifter in I think that's it for the bottom half of the crank case. Next up is the top half, apply sealant and bolt the two halves together.
 
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Here's the oil seal kit I purchased:



It seems to have everything I need minus the oil seal that sits between the starter motor and the engine.

Tapping the shift rod oil seal in:





More trial and error but I got the shift rod linked up to the shift cam:



Got the new starter bearing installed using heat on the case and cold on the bearing, tapped it in easily:



In order to drill out the screw that corroded itself to the housing, I bolted what I could of the starter to the case and used the mounting boss of the starter as a guide for my drill. Originally the case was threaded to accept a screw but because I can access the other side I'll replace it with a bolt and nut:



Cam chain guide and HY-VO chain guide in:



More trial and error here. .book says to do the idle gear, then the crankshaft, then the starter gear. That doesn't work. I did crankshaft, slipping HY-VO chain over starter gear and setting it into place, AC generator shaft through the starter gear, then last I did the idle gear and the shaft that holds it in place:



Then the little oiler for the HY-VO chain gets pushed in with some oil:



This piece supports the AC generator shaft at the other end and has a bearing integral as well as an oil seal and o-ring. The o-ring needs replacing, don't have that yet, but I went ahead and put the new oil seal in:





I might go ahead and seal the cases and bolt them together next so I can be done with the bottom end. I want to make sure everything is as it should be before I do that though.
 
This site has been instrumental in helping me match up oil seals. They have actual pictures of the oil seals themselves which show the #'s printed on the outer face of the seal. I've matched every seal I received in that kit and the only one I'm missing is the one that goes between the starter and the engine:

http://www.cmsnl.com/yamaha-xs400-maxim-1982-c-usa_model8882/partslist/

upload_2016-7-14_9-41-22.png


I erred earlier on the shot of the top crankcase half. I didn't realize the balancer shaft should be on the top half:



Reason being, there's a timing mark that has to mate up with the crankshaft:



I applied Permatex Motoseal to the lower engine case:
upload_2016-7-14_9-45-23.png


I used this stuff when sealing my Harley's cases and it seems to work well. Easy to apply and gives you about 5-10min to work with it before it stiffens.

I made my best guess as to where to apply the sealant and went to work:



The manual says you need it everywhere except to leave 2-3mm clearance from the bearings and to keep it out of the oil gallery "O-ring". That last part confused me since there aren't any o-rings in the oil channels. .at least I hope there weren't. I checked the parts diagrams and didn't see any and didn't see any grooves for an o-ring to sit.

To get the top case on is a bear. The crankshaft and balancing shaft are just sitting in the top half so when you flip it over they want to fall out. You need to secure them somehow to the top side of the top crankcase half. The manual says to use a wire, I used a couple zip ties through the cam chain which is around the crankshaft and around the balancer shaft. It was still a tricky operation but I was running out of time with the motoseal setting up so I just gave it a go.



Then it was more rushing as I had just bagged up the top and bottom case bolts (separately) without marking which one went where. There's 28 of the damn things in total. I decided to just get the top ones started finger tight making my best guesses, flipped it on its side and started the bottom ones. Luckily the bottom bolts there's only like 5 8mm and the rest are all the same length 6mm. Now that the engine is clean you can actually see the torque sequence # next to each hole which was a big help.

Shot with my bike in background:



Got the output shaft oil seal driven in using PVC:



It's starting to come together, feeling better now.
 
I had been deliberating on how to install the rotor. The manual says to use a special steering ring tool that engages around the rotor so you can torque the center bolt to 40 ft-lb. I almost bought one for $23 off eBay.



After spinning the thing around I realized I could put a socket on this drive gear nut on the opposite side of the engine and it would lock the whole flywheel (and consequently the shaft the rotor bolts to) in place. Using the breaker bar gave me the leverage I needed to hold everything.



Then to get the nut off I just used my electric impact. .which I've had to break out more than a few times on this rebuild.
 
Those oil seal kits are an absolute godsend! Too much shit to try and match up, I really appreciated having almost every seal I needed then buying the few that I didn't have.

Progress is looking really good, looking forward to seeing the rest!
 
Time to torque the clutch nut down. I didn't want to buy any specialty tools so i came up with this to hold the clutch from turning:



Then to do the primary gear i shoved a shop towel in the teeth:



Everything turns as it should. Almost done with the bottom end. I started wet sanding one of the covers. I can tell that will take a while.
 
I've been debating what to do with the cylinders so I finally broke out my micrometer and bore gauges. They're not big $$$ Mitutoyo's but they give me a good idea of where I stand. I zeroed the bore gauge to the micrometer set to 2.717" (69mm) which is the bore size of these cylinders according to the manual.





I think I set it properly since when I measured the very bottom of the bore the gauge read zero. This portion of the bore never sees the piston rings (piston doesn't travel the entire length of the bore) so it should be a good indicator of 2.717" or 69mm.

I was surprised to see there appears be no out of round or taper to either bore. Both bores measure about 2.7185" or 69.05mm taken at 90 degrees at 3 spots top, middle, bottom. The manual calls for a 69.1mm wear limit so these are about half way there. There's a shop in town that works on these older bikes I might get a second opinion, maybe I can get a fresh hone and new rings and call it a day. Possibly even re-assemble as is.
 
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