YAMAHA XJ650 RJ SECA 1982 POOR CONSUMPTION - cam chain?

Hi Xj
Further to my question, on purchasing this back in Aug/Sep 2011, and your subsequent replies (thank you!!), I now would like to know if, before I undertake adjusting the valve clearances, and the involved expense (?!) could I adjust the cam chain tensioner first, to see if that improved my consumption rate.
This bike is supposed to do 44 miles around town (to the gallon) and 59 miles on a long run (average is stated at 48.6)
I havent taken it on a long run as such yet, but I am only getting 30 miles to the gallon around town, and driving easy(and that is being stingy on the choke!!)
The engine starts first time, and runs well (acceleration etc) and there is no knocking sound or anything in the engine.
I think this is poor consumption(?)
I have no history of the valve clearances ever being checked, and also the cam chain tensioner either.
Will tightening the cam chain tensioner improve the consumption, before I have to adjust the valve clearances?PS. Forgot to add, the revs at operating temperature creep up to 1400rpm unless I turn the main headlght on, then drop down to 1100 rpm? (should be 950-1050 rpm?)
THANKS!

 

I would not expect a loose timing chain the cause that much of a problem, but get the valve check over and done with.

Its one of the foundations of keeping these bikes going properly.

 

The valve clearances needed to be checked at 3000 miles and every 5000 thereafter. Simply ignoring/putting it off because of "the expense" isn't doing your motor any good, and it sure as heck can clobber your fuel economy.

THE ONLY WAY to get the "rated" fuel economy (or anything close to it) with one of these bikes is to keep it in a good state of tune.

You can't do that by ignoring the basics; valve clearances are one of those.

Once your valves are in spec, then do a proper carb service.

 

Hello-A clogged/dirty air filter can cause poor fuel consumption. Have you inspected the spark plugs? They can tell you a great deal about the state of tune the motor is in. Just a thought, good luck.

 

I havent taken it on a long run as such yet, but I am only getting 30 miles to the gallon around town, and driving easy(and that is being stingy on the choke!!)



I'm just trying to figure out what "being stingy on the choke" means!! :?:

 

Thanks for all your feedback. Much appreciated! Valve clearances it is then! (will check air filter and state of plugs as well)
The idling screw is turned right down to zero in an attempt to get lowest rpm when at machine operating temperature, which still idles at lowest 11.000, creeps up to 14,000 when no lights on...
I have only had the bike since August '11, and there is no service history as pertains to tuning etc. (done 29.000+)
I know, I have read about after 3000 miles and every 5,000 miles thereafter valve clearances etc.
By the way, in answer to 'midnightmoose', "being stingy on the choke", in my case, is an English phrase, and I am referring to starting the bike, and driving off without using hardly any choke, to try and save fuel, when that is possible!!
In the meantime, any other contributions welcome....
Thank you all again!

 

Thanks for clarifying that. I've never heard that before and thought you were trying to use the choke while riding (Don't even think that's possible). So now that I know what it means, it raises another question. Are you really going to save THAT much gas by not warming it up? I'd think the damage you could do by running it cold is not worth the few drops of gas you'll save. Personally I let mine warm up before riding, but hell what do I know?

 

999-just had another idea here. Although you have been stingy on the choke, Moose over there is right-dont do that. Always let it warm up at least a few minutes before riding. Maybe your choke (cold start circuit, actually) is not closing all the way. Check the cable & actuator where it mounts on the carbs, to see if you have free play there. Good luck

 

Thank you!
Have checked plugs, cleaned and checked gaps, and all seem ok, except for no 1 + no. 4 cylinder plugs, which were only slightly sooty on one side (valve clearance?)
Both cold start mechanism cable, and throttle cable return to fully closed, with very slight play on inner when in that position. (idling is turned right down to 0)
As I have observed before, the idling rpm does read 1400 when machine reaches operating temperature, (should be 950-1050 idling at operating temp) and sticks at 1400 even if I put it in idling neutral.
The revs do come down, if I put in gear and slowly let clutch out and hold at the point of nearly engaging....I think you will remind me this a natural phenomenon!(?)
Having re-established these facts, it seems obvious to me that the +rpm when machine is in operating temperature, is contributing to my poor fuel consumption of only 30mpg short trips..........?
So, any other ideas, apart from the valve clearances, then carb synch, etc.?? (someone has just blogged in one forum that you save 25% fuel when you do fusebox change(!!!?) ?
Thanks to all......!
Regs.

 

I may have some other suggestions, but unfortunately the suggestions are ONLY valid if the valve clearances are OK.

You are at a junction on a flow chart that says;
Valve clearances OK? Y/N

The reason some experienced people seem to be pedantic about certain things, is because 'experienced' means they have been there.

It may not be a valve problem, but the time has come to find out.

On the bright side, if they are OK, checking, but not adjusting is a simple job.

 

paul.. a 30 year old bike that you have had for 5 months will need a lot of things to be checked out on it, especially keeping in mind your own safety. Plenty of info here on how to do the valve shims ... a good start to better fuel economy.

 

First , are you using Imperial gallons, or are you converting to 128 OZ gallons for us in the U.S.?? (The cost of fuel in England is about $10 a gallon !)

A "hanging or surging" idle is usually caused by an intake air leak (vacuum leak) notoriously at the throttle shaft seals (8), the air boots (cracks, gaskets, loose clamp, bad cap)

To find an air leak, I'd advise adjusting shims first, then a carb sync, spray a lubricant thru it's thin red straw, directed at the places above. The idle speed changes when the oil temporarily fills a crack. You can also use an UNLIT Propane torch - the idle may go up when the extra fuel is sucked in. If the whole intake track is buttoned-up perfectly, there will be no change in idle.

25% fuel savings for a fusebox upgrade?? How about 15% more horsepower from PODS !! :lol:

 

Stop beating your head against the wall. You're not going to find a "quick fix" because there isn't one.

The carbs need to be cleaned, inspected and properly serviced. Period. It's a given.

Then they need to be properly adjusted. Have to be, they have to work together.

In order to do that the valve clearances need to be in spec. NEED to be.

This isn't a matter of "ideas" it's a matter of necessity and a maintenance regimen that is KNOWN to work. Sure, there could be additional issues contributing to your symptoms, but these items need to happen first.

A 30-year old motorcycle isn't going to perform "as advertised" if it's in horrible need of basic maintenance. We ALL KNOW what that maintenance is, because we've been there; some of us multiple times.

The carbs HAVE TO BE attended to; then they NEED TO BE VERY PRECISELY ADJUSTED.

In order to that, the valves need to be in spec. Then and only then will you get a properly running bike that produces "as advertised" performance and economy. You're NOT going to find a solution other than what we've already told you; because we've told you what it will actually require.

Start here:

 

OK Thanks
I will check the valve clearances, when I have sold my other bike currently up for sale (Virago XV535 - UK 1990, 34,000 miles) and got the funds to buy shim holder, and replacement shim(s), if adjustment is necessary and replacement gasket.
I have downloaded and saved step-by-step for a Seca 550 from this site somewhere, and I have acquired XJCD from Dwayne...I believe I am capable of performing this task.
I have read that on Secas, the valve clearances get tighter when needed to be adjusted, rather than looser as on Maxims(?)
This would mean that any thinner shims would not be available directly from other cams on my engine (?), and I would have to access the 'shim-swap bank' that exists (?), or I have to pay upwards of $12 each for potentially eight (?) new shims (if intake, AND exhaust shims, need to be adjusted)
However, if as 'darkfibre' states, clearances are ok, I can bolt head back on and go on to the carbs.......only the head gasket to buy.
I have already 'sealed' boots of any cracks and still the same idling, but I would obviously test again with method 'timetoride' contributes after clearances checked...
Yes, I am using Imperial gallons in the UK which have 4.56 euro litres, to the gallon, (I believe?) and the current cost per litre is £1.36!! (£6.20p/gallon), and from 4.2 Imperial gallons down to turning on reserve, (0.8 gallon quoted) I recently got 121 UK miles, which averages at approx 30 miles to the Imperial gallon. (short journeys) (would this convert to much more to the USA gallon, and is that what the average of 44 -59 miles/gallon is quoted in specifics?)
Is this correct?
Regs.

 

The valve clearances tighten as they wear on Secas AND Maxims; the motors are essentially the same.

It has nothing to do with the shims wearing down. The valves pound themselves into their seats.

You don't need the valve bucket hold down tool to check your clearances; just a feeler gauge set.

You MAY be able to swap shims around on your motor to meet some of the requirements; they don't all have the same size shims installed to begin with and they wear at different rates.

 

Thanks bigfitz.
I'll get on with it......
Regs!

 

Your observed 30 MPG (Imp) would be 25 MPG here -
Many 550 owners report 55 MPG in good tune, where the "shafties" deliver 46, the difference being 100LB of weight, 1-200 CC's displacement, and a 3% loss in the bevel gears.

Oh, and your gas is only $8.18 a gallon currently - double ours, but don't you get free medical with that, or something?? :lol:

 

What maths are we using? On Pumba I did 1,000klms in 24 hours and recorded the klms(speedo and gps) and the litres on each fill.

ltrs per 100km?

By memory it was around 45- 55 mpg depending on heat or speed (in US terms the ride was 100 deg at 60-70 mph)