83 Seca 900 bogs down.

I just got a killer deal on a near mint 83 Seca 900 with 33k miles. I can't tell you how happy I am.

Unfortunately it has come with one noticeable issue. The bike seems to bog down when I open the throttle. It eventually gets there but with some hesitation along the way. I'll be at 70 on the freeway and if I open the throttle it's almost like I hit the kill switch for a second. The bike idles nice and revs nice and it doesn't bog down in the lower gears necessarily but from my experience I feel like it's lacking a little power. The actual bogging down is more noticeable at higher revs/speeds.

I just got the bike and haven't tried anything to fix the problem yet. Does anybody have any suggestions on what it might be. I bought it off the original owner and from what I can tell he barely rode the bike for the last 15 years. It just sat in his garage and collected dust taking it out occasionally. Any suggestions would be great. Thx

 

start with easy things. replace the air filter with a new o e m style, could be all you need

 

Hmmmmm, I wonder.

 

dirty , not that bad but if filter has been sitting for 15 years get a new one. eliminate it as the issue.

 

Make sure to send a pm to me so I can get it onto the 900rk database, or update a file.
Dfox

 

HI-FLO-FILTRO........that sounds like a quality part, they made covid 19 masks last week

 

Darn it. Just grabbed one off ebay.

 

Could I ride the bike without the filter for one quick ride to find out if that was the issue or not or should I do no riding whatsoever and wait for the filter?

On another note I heard only about 1200 of these bikes made it to the US. Is that true?

 

I sent a lengthy post to your inbox......

dfox

 

Bogging on throttle is a sign of lack of fuel. Take the filter out and go for a spin - no harm in it, but doubtful it will change anything. In theory it could be weak because you have a highflow filter, but I doubt it - maybe get a standard replacement?
Take tha carbs apart and have a look in the float bowls, but before doing that perhaps an hour with some clear tube to check float levels might be a good idea?

 

Bogging down has been solved. Poured a little seafoam down the carbs and voila! This thing runs smooth.

 

Could someone point me to a video or something on how to properly figure out how to put the wheels back on without the brake calipers rubbing on the rotor. I just changed the front and back tire but before I removed them I spun them and they turned as free as the air. Now when I put them back on they're rubbing all over the place. I don't know whether to secure the pinch bolts first or the axle nut first. The owners manual is extremely vague on this procedure. I only successfully done this once over a year ago but they were floating calipers and the 900 are dual pistons. Any help would be very much appreciated.

 

Pinch bolt is the last thing to do

 

Can anybody give me some good tips on how to get the mixture screws right? I'm about to synch up the carbs on my Seca 900 and I always have a hell of a time with those darn mixture screws. What's the secret to getting them right? I have the Gunson color tune and I swear, I never see a change in the color when I use them. So in the past, I just put the mixture screws at factory standard, synch the carbs from there and call it a day.

But with the Seca 900 I'd really like to give it a go and get it right with those mixture screws. I recorded what the PO has them at and they're all over the place. I do not know if this is where the factory put them or if he messed with them at some point. If anybody has some good tips that would be greatly appreciated.

 

Make sure you have no vacuum leaks first.....

 

I'm unfortunately getting the dreaded slipping starter clutch, can of rocks sound on my Seca 900. It has NEVER happened on a cold start since I have owned this bike, in fact, it very RARELY happens at all. When it does happen it's usually after I've been riding for a while and the grinding/can of rocks sound lasts only for an instant before the bike starts.

I've followed a few of the suggestion mentioned in other posts. I've removed the starter motor and sprayed carb cleaner down into the hole where the starter motor connects to. I ran Seafom in the oil for roughly 10 minutes at idle and then drained the oil for over 2 hours. I then changed the oil from the very popular Shell Rotella 15w-40 Diesel oil to 20W50 Castrol Motorcycle oil as I heard thicker oil can help prevent the problem and also it's been averaging pretty hot temperatures here in Southern, CA.

Also, when I removed the starter motor to spray carb cleaner I was able to turn the gear in there counter clockwise but was completely unable to turn it the other way (clockwise). However, I was able to wiggle it to and fro ever so subtly.

The other things I've done so far are a carb clean and carb synch, cleaned the rings on the alternator/rotor, changed spark plugs, new tires, new air filter, and valve check (all in spec).

I guess the real question is, should I be worried? What other things are worth checking ? Oh, and is the starter clutch different then the regular clutch? Thanks in advance for your help.

 

that is how the starter clutch works.
starter clutch is located where the starter goes in, the drive clutch is on right side where you put oil into bike.

you may need to wrap a little teflon tape around mixture screws . mix screw has spring then flat washer then o ring in that order.

mixture screws will be in different positions when set

 

I’m not too keen on the idea of trying to wrap Teflon tape around the mixture screws

 

+1 on this, I think there is very little room for error and how will that tape hold up to the heat and vibration? Having that tape get sucked down to the point of the jet might or might not happen.

 

I'm not quite sure what you guys are talking about. I'm referring to a slipping starter clutch and now we're talking about teflon tape on mixture screws. Someone bridge this gap for me.

 

you posted this and never said you fixed the issue

next post was this

so in answering the top post I suggested tef tape I will withdraw that and suggest some anti sieze to seal up threads of mix screw.
when you try color tuning cap off the mix screw you are adjusting to see if color changes. when looking for vac leaks spray some test fluid into the mix screws see what happens

if you feel starter clutch is going you have 2 options. ride till it goes or pull motor and change the clutch , look at chains and all guides while in there.

so where did you get on the color tune? next size up pilot jets is an option if you have to turn mix screws out to far. only do this when you are sure there are no vac leaks

 

I didn't get really any responses as far as the mixture screws so I just left them at what the PO had them at and did a carb synch. Bike is running fantastic. As far as the starter clutch, I'm just going to leave it for now. It only happens if I've been riding for a while, I park somewhere, and then turn on the bike. I'm wondering if it's a weak battery actually not having enough juice to give it a firm start. But like I said before, it NEVER happens on a cold start and I put some heavier weight oil in there 20w-50 and it still has yet to happen. At this point I'll just say the bike is perfect, except the handlebars. They're too narrow for me so I'm in the process of converting the top yoke.

 

I'm getting horrible gas mileage. I just came back on a 6 hour trip and I was averaging 25-30mpg going 70-75mph. I think this is kind of low. There are no leaks that I'm aware of. I turned my petcock to PRI to see if gas was overflowing out the back or the overflow tubes and there was no indication of that. As you can see in the plugs some are running a tad rich but would it make it so bad that I'm getting nearly half of the mpg as it should be?

 

1 good
2 lean
3 good
4 little rich
did you get it for economy or smiles per miles

 

I got it because it was cool.

 

Your post asking about the differences in our clutches. Motorcycle Starter clutch works like this



Motorcycle clutch works like this

 

Thank you very much for that. Really cool.

 

Just to make sure my coils and spark plug caps are okay I ohmed them out and the readings were as follows:
Caps
1-7.97(ohms)
2-4.8
3-4.6
4-8.11

Coils
1- Primary 2.8(ohms)
Secondary 11.85

2-Primary 2.8
Secondary 12.54

My only concern is with #1 and #4 plug cap as that is suppose to be between 4000 and 6000 and I'm guessing it wouldn't have much of an impact on my gas mileage. So I guess I'm opening back up those carbs.

 

Is there any difference in the rebuild kits between the 83 xj900 and the 85 xj900? Are the emulsion tubes and the slide needles universal or are they different lengths to fit the needs of their respective carburetor? I noticed that the jetting is the same between the different years but there may be other differences that I'm not aware of.

 

The '85-up XJ900 models used a different series of Mikuni carbs (BS36 vs. BS35 for the 1983-84 models); the BS36 series carbs have 1mm larger throats (venturi) and differ slightly in various ways. Of course, being BS-xx series Mikuni carbs, many parts are interchangable, but there are needle differences (the BS35 series used an adjustable-position main jet needles, while the BS36 series used fixed-position needles). The emulsion tubes are all the same. The vacuum pistons are different, with the BS36 version being quite a bit heaver than the BS35 piston unit, and it has fewer air-bleed holes.

 

Thanks Chacal. You sure do know your stuff. As far as the needle differences, are they the same length? Do they attach differently?

 

I just checked the float height on carbs 1 and 4 using the clear tube method. I think they may be too low. What do you think and what's the drawback of having them too low?

 

Can run lean sometimes... Could starve if you’re heavy on the throttle....

 

so you do agree that they are kind of low?

 

You’d have to do a fuel level check

 

On the matter of your brake pads rubbing on the rotors you can slacken the bleed nipple on each caliper and push the pistons back slightly then close the bleed nipples. Then keep an eye on the master cylinder fluid level when you pump the handlebar lever when the wheels and calipers are back on and everything is bolted up. Fit the wheels and then refit the calipers, with the piston pushed back slightly they will not rub on the rotor. Suspend the calipers with a wire hook or strong string out of the way until you get the wheels on.

 

When checking them on the bike you need to check the level in the clear tube at the center of the float bowl as the carbs are tilted forward. The carbs should also be level from 1 to 4 when on the center stand and on a reasonably level surface.

 

I figured it out. It was actually calcification of old brake fluid in the calipers preventing the pistons to move freely. Once I scraped all that away the calipers worked superb. Thanks for chiming in.

 

Thanks for responding. I'm still a little bit confused. What do you mean by the center of the float bowl and what is this picture explaining?

 

It seems to me and from the illustrations that I've seen that the fuel level in the tube should be equal with the bottom lip of the float bowl. NOT the top lip where the bowl meets the gasket but the bottom lip right where the screws are. If that's the case my Carb 1 is spot on but Carb 4 is off. Correct?

 

The picture is from the FSM showing the method to wet check the fuel level of the carb on the bike. The general consensus is wet set needs to be done off the bike where the carbs can be leveled, however if you check them on the bike then the tube needs to be near the center of the bowl as depicted in the picture and not at the very back as you had done. It is also gets a bit more convoluted as the shape of the floats will affect the level of a tilted carb, so again why the consensus is off the bike with a level rack.

If you need convincing then put some water in a clear glass and take a sharpie and mark the level at the center of the glass, then tilt the glass on axis with the mark and note how the level at the center does not change but moves up and down at the front and rear. You can also note with tilted carbs if you move the clear tube from back to front the level of the fuel in the tube will change going higher as the carbs are usually tilted down.

 

if the fuel level was low and leaning the mixture, the plugs wouldn't look like they do

 

Thank you for taking the time to explain that. Makes perfect sense.

 

With Hogfiddles help I think I found the possible culprit to my low mpg: worn emulsion tubes (see pic) I got rebuilt kits and installed brand new jets and tubes. I also spent an entire day working on the float heights (clear tube and height check) which were all over the place. I did not replace the slide needles though. When everything was said and done I clocked 100 miles at the halfway point which is a 25 mile improvement and 30 of those miles were city miles. I’m not complaining but not sure if The bike is working at it’s full potential yet. Throttle response is crisper though. I use to have a slight hesitation when I opened the throttle on the freeway possibly from running rich but that has pretty much disappeared. Also, I'm currently running heavier weight oil (20w-50) because of the hotter temperatures. Would this have an effect? What do you think?

 

So, I have to crack open my engine in order to fix the starter clutch. Never done anything like this before. For the most part there is never a problem starting the bike. It's usually after the bike is thoroughly warmed up and then I start it will the starter clutch start slipping. This happened the other day on a 7 hour journey where I pulled off for gas and after filling up the bike would not start. It just kept spinning and spinning. Luckily after the 7th attempt it started and I drove my ass home.
I thought about buying a boroscope and dropping it in from where the starter motor connects to inspect. I'm kind of hoping that maybe there's just enough sludge built up somewhere and that if I can spray some sort of cleaning solvent (SeaFoam) I can remedy the situation. But I think this is wishful thinking. I have already tried throwing SeaFoam in with the oil and running it for about 15minutes then drain. I've also tried thicker oil 20w-50 and that didn't help. I tried servicing the starter motor and also using the starter motor from my 650. Nothing worked. Gotta go in. Any words of advice before I kill the bike I love?

 

Send the 900 to me

 

Starter clutch replacement. Do alternator chain guide and timing chain (if required) here is a guide by CDs.


https://xjbikes.com/forums/threads/xj750-engine-removal-and-split-pictures.38545/

 

Spraying carb cleaner toward the starter clutch will clean out any crud. Make sure that the starter motor brushes are in spec, and that the motor is free of exessive carbon dust. The battery should be load tested as well. Do all of that BEFORE splitting the cases.


FWIW...they aren't so bad to push start, so parking upslope could save you a lot of work.