Too much engine oil, gear selection - 1981 XJ550

Hi all,

I'm Blakes from the UK. This is my first post and per the norm for first posts its a technical issue!

I've just got my 1981 XJ 550 running - its been almost fully restored (by previous owner) but had been sat for almost two years. So I took the carbs off and gave them to a guy from work who has far more experience of that kind of thing than me.

Yesterday I put them back on and eventually got it running. It seems to run well although not so much in the high rev range. Perhaps just wants used a bit more as I've had it running for no more than an hour. Anyway....

The main issue is that its fairly obvious that someone has put far too much engine oil in - that would explain why its chucking oil back out of the breather, right? Ok - easy solution, drain some off (will do when I get chance)

But also shifting gears is really quite difficult - more so when trying to change down, and neutral is almost impossible to find.... my main question here is - could this be related to the fact there is too much oil in?

Thanks in advance.

Will introduce myself properly in the 'lounge' and post up a pic of my bike for you all to see!

 

Hello Blakes..does th oil smell like fuel if you take out th oil fill cap, it's a common problem if th carb floats/needle isn't sealing, if it does your carbs need to come off.Could just be overfilled. Drain it and put in 'motorcycle' oil without th friction modifiers, they can cause clutch problems.There's a sight glass in th clutch cover near th brake peddle, level needs to have a slight gap at th top, check it on th centre stand.

Gear shifting is very unlikely to be related to high oil level, more like wrong oil or a clutch fault..adjustment a good place to start th process. Welcome to th whirlpool.

And have a look here http://xjbikes.com/Forums/viewtopic/t=1 ... art=0.html

 

Your carb guy may not have known how to properly set the float levels; which could cause fuel getting into the crankcase making you think it's "overfilled."

It could also cause poor running at any RPM.

Check your crankcase for a strong odor of gasoline; if it smells heavily of petrol it's not overfilled, it's dumping fuel into the sump.

Mikuni float height spec is +/-1mm, "below from the carburetor mixing body edge." Quoted directly from the book.

What they mean is 2mm +/-1mm below the seam between the carb body and the float bowl.

(Measure to the meniscus of the fluid in the tube.)

There is a diagram in the PDF for setting float heights; the spec is different between Hitachis and Mikunis http://xjbikes.com/Forums/viewtopic/t=34781.html

There's more to carb service than just cleaning and slapping back on the bike.

It starts with getting the carbs truly, religiously, dentally clean. Here's an exploded Mikuni for reference: http://xjbikes.com/Forums/viewtopic/t=31061.html

-Clean carbs, ensure they pass the "clunk" test.
-Replace hardened/disintegrating o-rings, clean float valve seats, etc.
-Set float levels using fuel and clear tubing, specs as above.
-Bench sync. Pilot mixture screws at 2.75 turns out to start.
-VALVE CLEARANCES IN SPEC. If they aren't you won't get a good sync. Don't skip this because it seems difficult, it's not.
-Running vacuum sync with YICS blocked.
-Tweak mixtures as needed (ColorTune or by ear using the "idle drop" method.)
-If you made any major mixture adjustments, re-check vac sync.

Complete the above, IN ORDER, and it'll run fine. Skip any or try to shortcut the process and you'll keep fighting with it until you do it right.

Honest.

Your shifting problems are symptomatic of a dragging clutch; which can also be greatly affected by the oil you run (or by a large amount of fuel in said oil. See above.)

 

Thanks guys, I'll see what I can make of it.

 

Right - the oil does smell of fuel... Looks like the carbs are coming off again

 

Funny - if my carbs overflow, the petrol comes out of the back and pours out of the airbox pipe.

Opinions are divided on the effects of friction modifiers on wet clutches, but I reckon that if a clutch is marginal, it might make a slip worse. I've never had a clutch drag because of the wrong oil, unless it was old and black. Maybe petrol would affect that.

If it's been sitting for a couple of years and the oil is suspect, I'd be tempted to change it regardless and see if he problems go away. A tenner on oil is not a bad punt to avoid stripping the carbs again. My experience is that float needles sometimes stick when the carbs first go back on, but once running settle down.

 

If the "carb guy" was ignorant to the exacting float level spec which on the Mikunis has a +/- 1mm tolerance, it won't run right. I've been taught this lesson twice now, by two different racks of BS28s, and they are BITCHY. That bloody one millimeter matters.

And you're right about it puking into the airbox, but at the same time it's pouring down the intake tract.

This is about the third or fourth thread running right now by somebody who had or was told the carbs had "been done" by somebody else and just can't figure out why it's not running right. What a surprise.

A lot of people who claim to know what they're doing really don't; or aren't aware of the adjustment specs that are so important. The only way to know everything's right is to do it yourself; use the clear tube method to verify the float levels. Then if they're fine, no adjustment required, probably just a REAL cleaning and a re-check.

THEN on to a proper sync so it idles, responds to throttle crisply and doesn't "hang" once the throttle is released.

A thirty year old clutch will need service; if the plain plates are rusty it will drag AND then slip because the friction plates are now linoleum.

The clutches in the 550/600s are more fun than their larger counterparts: http://xjbikes.com/Forums/viewtopic/t=29541.html

Use motorcycle-specific conventional oil such as Castrol 4T; 10W40 when it's chilly; 20W50 once the weather warms up.

 

Cheers guys. Might try a cheeky oil change first before taking the carbs back out..... Gotta be worth a shot and it will want done anyway.

Theres a pic of my bike here http://www.xjbikes.com/Forums/viewtopic ... tml#317866

 

Changing the oil won't set the floats nor will it sync the carbs.

The carbs aren't going to sync until the valves are in spec.

If the float levels are off it's a good possibility you'll simply "pollute" your new oil.

You said you "can't quite get it running right." FOLLOW ALL the advice given and it will run fine.

Right now you're "dabbling." And you won't dabble your way into a solution, trust me.

Do it right so you can enjoy, rather than be frustrated by the bike.

 

Your right bigfitz, watch this space.

 

There's only one way to do a job (except at the side of the road) and that's to do it properly, if you don't want to have to do it again, but sometimes jobs don't need to be done. If tapping the carbs frees off the float needles when the carbs are first used, then that's great. If problems continue then the carbs will need to be opened up.

If you have oil that is several years old and contaminated, then it's worth changing before you do the diagnosis. If contamination is a problem, then the second oil change is even more necessary to completely change the oil. (And even more so if your clutch plates were rusty and this has been scraped into the oil.)