Fuel L/100km | GTAMotorcycle.com

Fuel L/100km

Hi all!

Relatively new rider here and I just bought a Yamaha Radian YX600 1986. It runs great and have had no issues with it so far. However there is one quip with it so far.

As per the manual, this tank is supposed to get 5.4L/100KM on a 12 L tank. So you should get around ~200km per tank. I am only getting 80km. I'm not reving it or riding really aggressive.

The bike has 4 carburetors (in line 4) and the small plunger pins in all 4 carbs were stuck up when the choke was off (this however was rectified and they are all sat all the way in now when I ride; idle speed 1400~ revs). I don't mean to sound like a dumb new rider, I am just a little perplexed at the moment, any ideas?

One idea was to use carb cleaner and do that, but it seems unrealistic that it would get me another 50km's at least?

Thanks,
Alex Beckwith
 
30 year old bike will not get the MPG of when it was new
but 80km/tank is a problem
how's the air filter?
does it burn oil - blue smog?
can try a carb cleaner, like SeaFoam
if after trying the simple things
and you don't think the engine is worn out
I'd take the carbs off and rebuild

edit: Radian is a cool bike, it's worth getting working properly
spark plugs are easy to remove on that bike
take them out and see what the deposits look like
will tell you a lot about what's going on with the fuel burn
 
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It's quite possible on a bike that's 32 years of age that the carbs will need an off-bike tear-down, ultrasonic solvent cleaning, float check and adjustment and balancing. As well, the rubber couplers that connect them to the head and to the airbox should be checked as well.

Have other checks been done on the bike, like the valve clearances, ignition system checks and adjustments etc? How easy is it to push the bike (i.e. has the passage of 32 years led to stuck piston(s) in the brake calipers and drag?)
 
Have other checks been done on the bike, like the valve clearances, ignition system checks and adjustments etc? How easy is it to push the bike (i.e. has the passage of 32 years led to stuck piston(s) in the brake calipers and drag?)

This is a good suggestion, it will be easy to check. Bad chain, stuck brakes could cause this. The rear drum brake is practically Flintstone technology, but it could still be seized too.

Radian is a cool bike (well ok, I think it's cool... it's definitely FUN when running right), sounds like this one needs some attention which isn't much fun for a new rider. The upshot is that it is a very easy bike to work on, so if you have the time to spend to learn then you will likely be able to fix it.
 
Something doesn't add up...by my calculations the bike is averaging 15L/100KM.

I'd be surprised if that's even physically possible unless there's a seized brake or something major binding in the drivetrain. Other than that the engine would have to be running so slobbering rich that you'd almost have raw unburned fuel spraying out of the exhaust...or your pipes would be cherry red. That's a LOT of fuel - in comparison, my old Hemi Magnum V8 used about the same amount of fuel per 100KM in the city.

Are you SURE it's actually using that much fuel? Have you filled it, gone for a ride for 50KM and then filled it to the same level again? Exactly how many L does it take to refill the tank at that 50KM mark?

When you say you're only getting 80KM...what happens at 80KM? Does it run out of gas? Has a previous owner put a gage or something on it that's making you think the tank is empty?

My point is...we need to make sure that it's actually using that amount of gas, calculated liters put in the tank per kilometer driven.
 
Has it been modified?
 
Okay so a lot of feedback!

So here is what I have checked!

1. The air filter is new and has a slight (very minimal) smell of fuel.
2. When I spin the front brake it seems stick on the calipers to the point is barely makes 1 rotation (working on that now)
3. Here is the big one...On the right exhaust, there is a constant very small splutter of oil and at higher revs slight blue smoke (so burning oil).
-This however might be due to the oil level on the bike being almost double what the manual reads (doing an oil change this weekend) and I had read that bikes sometimes burn extra oil in the combustion.
-No static dripping of oil, only when running and only from the right exhaust (so the two right cylinders)
-Bike runs smooth and fine
4. As per fuel, I fill her to the tits, then reset my trip. Without fail, at 82.xKm the bike starts to chug and without a change to the reserve will cut. I haven't risked running the reserve long but there isn't a lot a fuel at all in the bottom.
5. I have carb cleaner and am doing that on the weekend, will post results.
6. Spark plugs on the left two cylinders are more or less clean and dandy//two right ones look to be a little black.
7. Very easy to push the bike, I imagine it will get easier to push when the brakes are adjusted

I am fairly new to the technical side of things so I am a little weary of a tear down. I would however be very open to buying a nice case of beer for anyone who wants to try it and let me learn in the process if need be! I am loving the bike, it's a sweet first bike and want it running and getting good KM's I just need the help

I can take whatever pictures you guys need no problem, just let me know and again, thanks for all the input, this community keeps showing me who great it is!

Thanks,
Alex Beckwith
 
Okay so a lot of feedback!

So here is what I have checked!

1. The air filter is new and has a slight (very minimal) smell of fuel.
2. When I spin the front brake it seems stick on the calipers to the point is barely makes 1 rotation (working on that now)
3. Here is the big one...On the right exhaust, there is a constant very small splutter of oil and at higher revs slight blue smoke (so burning oil).
-This however might be due to the oil level on the bike being almost double what the manual reads (doing an oil change this weekend) and I had read that bikes sometimes burn extra oil in the combustion.
-No static dripping of oil, only when running and only from the right exhaust (so the two right cylinders)
-Bike runs smooth and fine
4. As per fuel, I fill her to the tits, then reset my trip. Without fail, at 82.xKm the bike starts to chug and without a change to the reserve will cut. I haven't risked running the reserve long but there isn't a lot a fuel at all in the bottom.
5. I have carb cleaner and am doing that on the weekend, will post results.
6. Spark plugs on the left two cylinders are more or less clean and dandy//two right ones look to be a little black.
7. Very easy to push the bike, I imagine it will get easier to push when the brakes are adjusted

I am fairly new to the technical side of things so I am a little weary of a tear down. I would however be very open to buying a nice case of beer for anyone who wants to try it and let me learn in the process if need be! I am loving the bike, it's a sweet first bike and want it running and getting good KM's I just need the help

I can take whatever pictures you guys need no problem, just let me know and again, thanks for all the input, this community keeps showing me who great it is!

Thanks,
Alex Beckwith

I'm no moto mechanic, but having your oil overfilled is bad - doubling it, I can't imagine it would make it better.
 
Extra oil is not good. lots of parts making it foam up. Not sure the extra drag of parts going thru all that oil would create enough drag to lower the mileage though.

OP, you're putting close to 12L each fillup? That was a downside to the Radian, small gas tank.
 
sounds like the old girl needs some basic maintenance / attention. engine wise I would;

Remove the carbs, clean (unltrasonic cleaning/cost is not necessary) replace the float valve seats and needles, adjust float heights to spec. check main and
pilot jets to see that they are OEM sizes. sync carbs AFTER valve clearances are set. adjust idle speed.

new plugs

Adjust the valve clearances to spec and reset cam chain tensioner (if manual).

I would think that the oil burning is likely from worn and old valve guide seals on a bike this old...might be ok for a while if its not burning(smoking) oil too much. curious why you would even start the bike with the oil double full?

best luck.
 
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QUOTE: I am fairly new to the technical side of things so I am a little weary of a tear down. I would however be very open to buying a nice case of beer for anyone who wants to try it and let me learn in the process if need be! I am loving the bike, it's a sweet first bike and want it running and getting good KM's I just need the help

Thanks,
Alex Beckwith[/QUOTE]

Hey Alex, post your general location for potential help.
 
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I'll try out those suggestions. First im doing the carb cleaning. @boyoboy im in St Catharines! So i'll manage an oil change as well then. As per all the suggestions for repairing the carb and all, I am not quite that confident so i'll have a lot of reading to do or someone to find haha

Thanks,
Alex
 
Once your bike is running right, you will want to use reserve a lot... it's like a third of your range lol. If I had another one I would probably modify the petcock, file down the primary fuel thingy so reserve becomes like only 20% of the tank.

Anyway! boyoboy, cam chain tensioner is semi-auto. Does require servicing, but it's not much work.

OP, mind that you put the oil filter together correctly. There's at least four ways the bits will fit but only one is right... a bit of a dumb design. There's no guarantee the last person got it right either. It goes on the union bolt in this order: filter housing, spring, washer, filter. The flat side of the filter faces the engine... I think

If your oil is really that badly overfilled, make sure to look at the air filter. If there's much oil on it you'll need a new one. Hah, I might actually HAVE one! Will take a look
 
[[[UPDATE]]]

So I took all the oil out, inspected it (no metal fragments at all just some carbon pieces, not a lot). And replaced it to the correct manual specified amount of oil. After which I used the carb cleaner a few times and that went without issue.

After a quick test ride, there is NO MORE oil coming out of the exhaust. So I think it was just the excess of oil. Also, the bike felt a lot more responsive after the carb cleaning. Hopefully this improved the fuel mileage but I guess time will tell.

As per the other questions, the spark plugs on the right were blacked but not wet. just old plugs I think so i'll grab new ones tomorrow. The air filter is clean with no oil also. What were some of the other suggestions
-carb tear down (I am not yet confident enough to do this)
-my buddy also suggested putting the petcock in a slight half on position to "duck-tape solution" the fuel usage a bit.

The last issue that I think I can tackle with help would be just loosening up the breaks slightly. They still rub on the front only and I don't want to touch the breaks until I know how to adjust properly....Attached is a picture of the front break if any of you know!

As more ideas or offerings of help? You guys are honestly rock stars for me thanks again.

Thanks,
Alex Beckwith

abaN1o4.jpg
 
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Well, if the oil was so overfilled that it was puking out the exhaust there was no way it was running effeciently. Might certainly have had a lot to do with things to start.

Carb cleaning is never bad. Things like seafoam and the sort will help but cannot replace a good teardown and rebuild. If you've never done a carb cleaning before there's lots of tutorials online (YouTube and such), so order the parts now - a rebuild kit will include new needles, gaskets, seals, possibly floats, etc.

If you're not sure what you're getting into, take them to a professional. If you're in the Oshawa area I know a place with a carb guru, bar none the best.

-my buddy also suggested putting the petcock in a slight half on position to "duck-tape solution" the fuel usage a bit.

Yeah, don't do that.
 
As for the front brake, it's a disc. There's no real adjustment, if it's sticking on it means the caliper needs to be serviced or replaced because the piston isn't retracting fully when they are released.

A slight drag on the front wheel isn't uncommon between the brakes, wheel bearings, etc.

A quick test to see if brake drag is serious or not is to get on the bike when everything is stone cold and go for a 10-15 minute ride at speed without using the brake you want to check whatsoever....so if you're checking the front brake for drag, ride and stop using the rear brake ONLY. When you get home, carefully feel the front brake rotor - it should be cool to the touch. If it's not, you have a dragging brake.

Be careful riding using rear brake only - you only get 20% of your braking effort from the rear (and it's easy to lockup) so you need to ride accordingly.

To check the rear brake, do the opposite - from stone cold, 10-15 minute ride at speed using only the *front* brake to stop, then do the touch test on the rear drum.
 
no adjustment on the calipers

pistons will be pushed out hydraulically as far as they can go
when you release the lever and the pressure drops
it's the distortion of the piston seal returning to normal
that drags the piston back into the bore a bit
that is if everything is clean and moving freely

if the pistons are rusty or all crudded up
they may not retract properly
 

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