To Rebuild or Not to Rebuild

Has anybody out there ever rebuilt an 81 xj550 Seca Engine. I have one that's running...okay, but I also have access to one in a junk yard for 350 bucks. Was thinking of doing a complete Seca teardown and restoration taking the best of both bikes and going to town. However, to really make it worth it I feel I would also have to rebuild the engine otherwise you're just slapping old parts together. I am a novice mechanic and this is my first venture into bikes. The 81 Seca is one of the sexiest bikes I've ever seen and I really want to go for it. Any vids, tutorials, articles would be very helpful. Thanks. Josh

 

first consideration is the amount of money you are going to spend. Complete restoration is a costly project.
what milage do you have on motor? test the compression. all you should have to do is rings and valve job.
consider that the valve job is usally just a refurbish of the head

ground up rebuild of motor would have you spending money you do not need to.

 

Thank you for responding. Money is definitely an issue since I want to do it myself. However, I like your idea of just doing a rings and valve job. Are there any tutorials you could direct me to? Thanks.

 

How many miles are on the engines?
A runner typically won't need to be rebuilt, and there are many things that need to be checked in order to determine if the rebuild is necessary.
There is also the issue of parts avaliabllity. So few of them have needed rebuilding that Yamaha stopped providing pistons, oversize piston rings, and plain bearings a long time ago. Anything you find now will be from someone's stash of NOS parts, or from an engine that's being parted out.

 

Got it. Unfortunately, I don't know the mileage because the studs on the metal ring that make the speedo wheel turn were bent. Wish I knew that before I bought the bike. Nevertheless, this bike has had a full life, I'm sure. I only got 96 miles on a full tank. Most of that was city driving but I'm guessing I won't get much more then that on the highways. If I do a top end rebuild or any rebuild for that matter will I get better gas mileage or am I just stuck with a beautiful gas guzzling machine from the 80's.

 

you should get 45 to 50 mpg out of the city

 

I'm not sure if it will. As it stands I'm only getting 25.

 

yes but how much 6th gear time do you get in the city
and once you get shims in spec and carbs cleaned and tuned your milage should improve

do the compression test see what you get ( should do this after shims)

90% of my riding is 55 mph and above

 

Pardon my ignorance but are there any tutorials you could direct me to on a compression test.

 

From the Information Overload Hour:

https://www.xjbikes.com/forums/threads/the-information-overload-hour.27544/

- COMPRESSION TESTING:

Yamaha recommends that you perform a compression test every 5,000 miles or so, and that you should record the readings, per cylinder, for future comparison and evaluation. The acceptable readings (specified at sea level) are as follows:

To do a compression test properly, you should first make sure all of your engine valves are properly adjusted to their recommended clearances, as valves that are too "tight" (not enough clearance) will allow the intake or exhaust valve to be open more than is necessary, or at the wrong time within the compression stroke cycle, thus bleeding off compression that would otherwise be developed.

http://www.xjbikes.com/forums/threads/compression-test-xj650.113151

Do not use thread adapters or the like on your pressure gauge, as the added volume of air space within the adapter will reduce the indicated pressure readings.

a) make sure the engine is warm (at operating temperature).

b) remove all spark plugs, and then stick the plugs back into their caps and make sure the plugs are grounded to the cylinder head (or even better, disconnect your TCI unit).

c) remove the airbox filter lid and the air filter.

d) make sure the battery is FULLY charged, and remains so throughout the course of these tests! It is actually recommended that for purposes of compression testing that the TCI be un-plugged and jumper cables to a large capacity battery (i.e. car battery) be used to make sure that the cranking speed remains pretty constant between each reading. Slow or sluggish cranking speeds will reduce the indicated compression pressure. Yamaha specifies their compression pressures at 300 rpms (which is why the battery needs to be in good shape).

e) open the throttle FULLY and keep it open during testing.

f) crank the engine over until the needle stops advancing.

g) Let the starter cool down for a minute or so, then do the next cylinder, etc.).

h) If the readings are below spec, then shoot about a teaspoon amount of motor oil into each cylinder, crank the engine over a few revolutions with the starter (to spread the oil around), and then re-test each cylinder using the above procedure.

i) compare the two results and analyze.

j) keep all of your figures, and note the date and mileage from your odometer, so you can compare the next time you take readings (every 5,000 miles or so).

 

Hey Josh, I just bought the 81 SECA, the first bike I had in college and was wondering what you did to your bike? I might have to redo the seals and gaskets since there was a lot of oil and grease over the outside of the engine.
Also my engine revs high on start up. Might be a vacuum problem.

 

Please start a thread for your bike.
His bike is not your bike.
His problems are not your problems.

 

Sorry for the blurry pic. I'm having an oil leak out of this little drain hole. Does anybody have any idea how to fix this?

 

Remove that cover. Behind it you will find the ignition pickup and reluctor. Behind that is the seal for the crankshaft. That is where the leak is coming from.
Chacal has replacements that do not require splitting the crankcase to install.

 

Just be very careful not to damage the pick ups themselves or the reluctor

 

Is this the part you are referring to:
HCP18762 Aftermarket crankshaft flange OIL SEAL, fits on the left end of the crank to the case on all XJ550, 1984-85 FJ600, 1986-87 FZ600, 1986-90 YX600 Radian, 1992-98 XJ600 Seca II, XJ650, XJ700, XJ750, and XJ900RK, RL, N/FN, F, and S/SH engines, and on the right end of the crank on XJ1100 and XS1100 engines. Use 1 per engine. NOTE: Approximately 1/2mm thicker than original seals and is metal-shielded (unlike the original).
$ 11.95

 

I think so, but start a conversation with @chacal to confirm.

 

Would anybody have some ideas on why my bike is having a bit of trouble getting into first gear? At first it was a little sporatic but now my Seca 550 is consistently having trouble getting into first to the point that I have to really stomp on the gear shift lever to move down into first. I use to be able to comfortably push it into first gear now I have to bring the weight of my entire leg down on the petal to get it into first from neutral. When I start to take off it will sometimes have trouble catching and I can't take off as quick as I use to, almost like trying to start in 2nd. it even pops a little bit more. I first noticed something was fishy about two months ago when sometimes I would shift into second gear and it would often get hung up into neutral and then I'd have to shift again to get it into second. All the other gears work fine after that.
The only thing I've tried so far is adjusting the clutch cable of course and no matter if I make it tighter or looser it's still a bit of a struggle to get down into first gear. Any ideas would be great. Thanks.

 

Pull the shifter cover. Look for any bent/broken parts/springs etc. Also look for broken bits of plastic. It could be from the alternator chain guide breaking up. With the bike up on the center stand, not running, can you shift through the gears without excessive force? You may have to rotate the rear tire to get it to hit all of them since it's not running. Maybe you need a clutch

 

How you adjust the clutch cable matters.
Clutch Adjustment & Clutch Cable Replacement Procedure

Having said that, I agree about perhaps needing new friction plates.
One simple test is to get on the highway in fifth, then shift down to third as if you were going to pass a car. Any clutch slippage will become quite obvious at that point.
Do that test after adjusting the cable.

If there is no slippage of the clutch, and the cable adjustment does not remedy the engagement problem, then you most likely need a new clutch cable. They do stretch a bit, and a bit is enough to keep the clutch from fully disengaging.

 

I changed the oil and adjusted the cable on a cold bike to 3mm free play as per the manual. It works fine now. It may have been a combination of bad oil and not enough free play.

On a different note. How do I get this thing OUT!!!!
This is the left crankcase flange oil seal. As you can see I have made attempts at trying to pry it out with no success. I tried screwing in a wood screw and then yanking it out and it is in there tight! Can anybody give me some helpful hints on how to get this seal out. thanks

 

You will need to very carefully cut a wedge out of the steel part of the seal (a Dremel tool or smilar), and use a chisel to very carefully curl the seal to a smaller daiameter so it can be removed.
There may be other methods that someone else can chime in on.

 

That's exactly what I did and that got it out. The very carefully part is in question, however. I actually just used a nail and hammer to start a hole, then used a flat head screw driver and hammer and made an incision into it. That was able to collapse the seal just enough that I could pull it out with brute force.

 

I'm not sure who decides to delete threads but I wanted to start a thread about this since there is almost no information regarding how to do this procedure on here and the next person who has to do this could find it easier on this site. Maybe I should've explained that before. Just an fyi.

 

If you can do a writeup in the DYI section that would be appreciated. Include photos or drawings if you can.

I deleted your post as it seemed to be asking the same question as you were asking here.

 

So, I filled my tank up the other day and I accidentally filled it up almost to the brim. Not thinking anything of it, I quickly returned home and parked my bike outside, covered it and that was that. A couple days later I go to ride and the new paint job has been destroyed. Looks like gas somehow oozed out. It's been 90+ degree heat outside. I should also mention that I put a new gas cap on it and it's very hard to put on. Meaning, I really have to press down hard before the key will turn back to secure the cap. I'm wondering if the heat and putting too much gas in the tank made the gas ooze out? How the hell did this happen?

 

fuel expands when heated

 

Would this have been avoided if the tank were only half full?

 

It would have been avoided if you had stopped filling the tank when the fuel was even with the bottom of the collar inside of the filler neck.
I wonder if the gas cap vent might not be blocked.
Your Gas Cap and You

 

I guess another question to ask is if it is bad to park the bike in extreme heat or not regardless of my tank situation. Can prolonged exposure to heat destroy a bike pretty quickly or does it matter?

Yeah, I kind of ignored my spidey sense when I started filling the tank so much. Should have just went out and put 15 more miles on the bike before I went home.

 

Heat is a factor in aging (hardening) rubber parts, as is UV exposure. The reality is that if you want to enjoy riding you just have to park outisde in the heat sometimes. Not anything to fret over. Just be sure to follow the maintainance schedule.

 

Word

 

Help! New fork seal still leaks.
I attempted to change my fork seals and the job seemed pretty straightforward, however, the same exact fork still leaks. Any ideas why this might have happened?

 

Do you have any pics of the fork tubes? Any pitting close to the wiper? What did you use to put the bottom whipper in? As you slid the fork tube in did you have a little lube on it?

 

I think I might know what the issue is. As you see in the pic there are nicks on the chrome that go into the lower shock. However, when I took it apart there were no visible tears in the seal itself. In any case, are these salvageable or do I need new forks?

 

Salvageable, but it'll take a bit of patience and work.
You'll need to use wet-and-dry paper to poilsh out as much of the pitting as you can without reducing the dimeter significantly. Use a dental pic to clean the rust out of the pits. Degrease the tube thoroughly, and then use a good 2-part epoxy to fill the pits and allow it to cure. Then follow-up with wet-and-dry paper again (wet this time). I start with 600 and progressively move up to 2000.

That's the economy way, and will last for many years.
The proper way is to sent them out to be filled, ground and rechromed. That costs a bit more.

 

I started to have a small idling problem with my Seca 550. Assuming the bike is warmed up and have been riding for a while, if I pull up to a stop light and let it idle in neutral, after about 10 seconds it SLOWLY starts to sputter out. Giving it a little choke does sustain the idle, however. I'm wondering if the carbs could be a little gummed up and I might need to run a little Berrymans through them? Any other thoughts?

 

you should adjust idle after riding for 10 miles or so.

it does sound like the pilot jets circuit is

 

Will do. I'm curious if the heat has an effect on the idle as it's been very hot lately.

 

yes cold air is denser than hot expanded air. more o2 in the cold air plus more expansion when fired in the cylinder

 

This will be hard to describe in words but I feel it might be related to my idling issue. When I first start the bike the engine makes a high revving sound and quickly goes away within 3 seconds. This sound is not to be confused with the engine itself revving high it's just a SOUND coming from the engine. When I'm out riding and I come to a stop it will make that same high revving sound but this time it will sustain it. If I open the throttle a little bit the sound goes down. Any thoughts on what's happening?

I checked the air filter and that's fine. I ran some Berryman's for 30 minutes through the carbs. I've adjusted the idle knob, spark plugs look good. I'm thinking either a valve adjustment or carb clean next?

 

Getting an intermittent screeching sound from my starter motor on my Seca 550. It first happens when I initially start the bike but quickly disappears and then comes back when I come to a stop. Sometimes it doesn't happen at all. When it does happen the bike starts struggling to stay idle. Very weird. I actually have a spare engine. Would it be worth a try to just replace the starter motor?

 

are you sure its not the alternator

 

I thought of that so I opened the alternator housing to check if anything was loose and rechecked the torque spec that holds the rotor in and it seemed to be fine. The sound is definitely coming from that area though and it ALWAYS happens right when I start the bike but quickly dissapears and then it comes back intermittently when I stop so, sometimes it happens and sometimes it doesn't. Really weird. What are you thoughts?

 

i was thinking something along the lines of alternator squeel. maybe check charging voltage when the squeel is happening. brushes look good?

 

I have always had an issue with the charging voltage on this bike. After 15-20 minutes of riding the bike slowly reduces its charging output. I tried tirelessly to try and figure it out. Some people were even telling me I don't have a charging problem. So, it's really difficult to identify that as a symptom of the problem but the bike has basically been riding fine for the last year or so. And yes, brushes look fine. The only thing that happens when the screeching happens is that the bike starts to struggle to stay idle. Perhaps you can educate me about this alternator squeal. Is that the result of the alternator rubbing against something?

 

is the brush holder new with the brushes?
thinking battery but that is new correct?

 

As I recall we covered the charging voltage and determined that the battery was charging. When the battery approaches full charge the regulator drops the charging voltage so the battery isn't cooked.

I think that the sound is the starter clutch grabbing and then releasing. That can happen when it has sludge buildup (or if the roller carrier has cracked).
A video with good sound would help the diagnosis, particularly since there are other moving parts in that area which could produce a similar intermittant sound.

 

Unfortunately, the charging system was never solved and is still weak. If I ride it for a few days without putting the trickle charger on it overnight then eventually the bike won't start. So, I just got use to putting the trickle charger on it every night. The battery has NEVER been fully charged from this bike.

As far as the sound let's say for arguments sake that there is sludge build up in the starter clutch. Are there any videos or tutorials you could point me to to remedy his situation. Even if it doesn't solve the problem it's probably a good idea to go in there and clean out all the sludge anyway. Thanks.