gas guzzling machine?

[Tzigane]

Hi everyone,

A few years ago I owned a GTR, which ran 1:17, 1:18. A trip through Norway, relaxedly cruising along with passenger and camping gear got the bike at 1:23(!)

My current GTR however, uses quite some fuel, last tank was at 1:14, before that, 1:15. I'm not a fast driver, rarely come above the 6000 rmp, and I'm happily cruising along at 110/120 km/h.

What can I do to improve this? The carbs have been synchronised very recently. Is there more I can do with them?

[DC Concours]

Not a gas guzzler.

I get about 40 miles/gal. average city riding. I assume a little better on the highways.

[George R. Young]

My bike gets around 42 miles per US gallon, or 1 liter for 18 km (1:18). If you're only getting 1:14 (about 33 mi. per US gal) there may be something wrong.

Possible guesses:
dirty air filter
brakes dragging
pilot jet too large
needles shimmed too high
floats set too high

[Tzigane]

Thanks!

Looks like I'll have to inspect the carbs a bit further!

A while ago I had a leaking petcock, which overflowed the airbox. Maybe an airfilter change could help things.
I recently rebuilt the brake calipers, so we can safely rule that out.

[Jet86]

gas in the airbox means stuck float/needle, look up Hydrolock here on the forum

[SteveJ.]

gas in the airbox means stuck float/needle, look up Hydrolock here on the forum

Do this really, really soon. You are courting a bent rod situation.(a.k.a. hydrolock)

[Tzigane]

I checked for hydrolock. At least I think so.

The situation was as follows:

- Buy bike
- drive to my girlfriend
- pick up girlfriend, refuel because I didn;t know how much was in the tank
- get home, see the bike leaking gas.

- remove tank quickly and fear for hydrolock
- check the petcock, petcocks leaks.
- next morning, I checked the oil. Oil level was still exactly the same as it was the day before. I figured it would be higher if there was fuel going inside the cilinders,.
- start the bike, (with the tank removed), starts and runs fine.

- repair petcock
- no leaking fuel
- bike has been running fine ever since, it seems.

This was about 800km ago. I haven't owned it for very long yet, so I'm now realising it uses quite a bit of gas.
I'm not actually sure whére the fuel came from, since it was dark, and I was just frantically removing the tank to prevent any damage.

I checked the filter today, is this bad enough to install a new one?


I'll do the bent rod check. I haven't gotten around to buy a key to remove the sparkplugs yet, how wide are the hexes of the plugs?

[throb]

18mm.....the plugs are seated quite deep, but if you take a 6 or 7 inch length of vacuum hose that will fit snugly over the porcelain portion of the plug, it will reduce your frustration level greatly getting the plugs out and back in.

[Tzigane]

Thanks! Great  tip too about the vacuum hose!

[RFH87_Connie]

Hydrolock takes TWO things to happen.  A leaking petcock (1) and something causing the float needle not to seal (2).  This could be worn or damaged needle or needle seats, weak needle springs, grit in the gas tank getting to the carbs, deteriorating fuel line, or any other similar thing.

As for your gas mileage, it could be that your needles aren't seating fully so they are giving you a little too much fuel when the bike is running.  Or, the needles need to be adjusted to re-set the carb bowl fuel height back down.  Over time from what I have seen is that the fuel height rises in the float bowls due to (I suspect) plastic floats slightly warping over years of use - It just takes a tiny bit.

You guys don't have oxygenated or alcohol added fuels do you?

The filter looks OK to me - maybe just wash it with gas and an air hose and put it back in.

[Two Skies]

Sometimes, simply draining the float bowls, then opening the petcock to 'prime' to flush out the needles and seat can clear debris out of the needle/seat.

I had this happen (was smelling fuel after parking the bike).  I grabbed a handy container, plus a length of surgical tubing (any appropriate plastic tubing will do), attached said tubing to the nipples on the float bowls, then drained each of the four float bowls individually while flipping the petcock to prime briefly each time.  Some visibile debris was in the large cup I drained the bowls into.

After doing this, gas mileage went back up and no more gas smell. 

If this doesn't solve your problem, yeah it's probably time to rebuild the carbs!

BTW, I get 42 MPH on average usually (can get 45 MPH on a good day if I lay off the throttle, and don't go faster than say 65 MPH).  Said mileage dropped down into the low 30s when my needles started acting up (due to debris).  I've since put an inline filter between the carbs and the tank.  Said filter needs to not be very restrictive, otherwise you may have fuel starvation issues.


Long term, though, you should look at Overflow tubes, to help stave off the dreaded hydrolock.  You are across the pond, so sending your carbs to Steve in Sunny Florida (Shoodabeen Engineering) might not be practical.

[SteveJ.]

Welcome aboard.

Air filter: This is reusable. Wash with soapy water(dish detergent works well), dry, then wipe lightly with engine oil, the manual calls for 30W.

SiSF has done carbbies from over the pond, shoot him an email for particulars.

[Tzigane]

Thanks a lot guys !

I'll try draining the bowls first, and if that doesn't help, I'll rebuild the carbs.

[Tzigane]

Hmm, I think I'd better do it properly.

What would you guys advice, a good cleaning with an ultrasound device, or get new needles/gaskets etc?

[gPink]

Most everyone would recommend you talk to this gentleman... https://sites.google.com/site/shoodabenengineering/

[Daytona_Mike]

Hmm, I think I'd better do it properly.

What would you guys advice, a good cleaning with an ultrasound device, or get new needles/gaskets etc?

Neither one of those. You need to ship them out. This is something you should not be trying for the first time. This is the best advice your going to get. Get the FULL carb service done. You will not regret it.
https://sites.google.com/site/shoodabenengineering/

If you want to know how to remove the carbs  it is all here
https://sites.google.com/site/shoodabenengineering/video-resources

[Tzigane]

Hah, thanks! Good videos.
Sending the carbs overseas to modify them is not really an option due to costs and time-restraints. I would if I could, but it would probably cost almost as much as half a new bike, and I'll be without much needed transportation for too long.

I think I'll open them up and clean them for starters. If that won't do the trick, I'll order the necessary replacement parts! Are there any good videos on cleaning our carbs, or checking the float levels?

I have done some work together with a good mechanic on the carbs of my previous bike, and at the garage I'm working at I'll have the help from a very good mechanic, so I won't be at it alone.

[Daytona_Mike]

You better at the very very least install over flow tubes because if you dont I predict you will ruin your engine.
I was reading your earlier post

A while ago I had a leaking petcock, which overflowed the airbox.

You were very close to hydro-locking that bike. do not do it again.
Just trying to help you out.  Why is it too much to ship?? Have you looked into it?  We have had many people send their carbs in for servicing from overseas.

Just another FYI- we have had others try and do their own carbs with mechanics and mechanical backgrounds because they thought they could save some money and started out with the best of intentions and confidence.. Mostly that  ends up with total failure and  costing them  way more to repair the additional damage.  Your questions tell me you should not be doing this yourself.
Not saying that is the case for you- just letting you know. Trying to save money on carb maintenance can and most likely  will cause you major grief and multiple carb removals and alot more money and major downtime. Please dont be that guy.
I do wish you the best of luck, I really do.

[Daytona_Mike]

if you do get into trouble, buy a used setup off ebay over here then have it shipped direct  to Shoodabeen. In this way you only have to pay one way shipping to you and then you can sell your used carbs over there.. Just trying to help out with options. Here is a cheap set

http://tinyurl.com/mg2egpn

[Tzigane]

Thank you for the advice! You're a great help!

Having a set shipped from the US directly to here might be a good option. I would indeed like the overflow options, seems like a must have. I'll consider my options!
I don't have much to spend at the moment, unfortunately, but a safety against a disastrous spending is also wise.

Regardless, I will order a petcock-rebuild set to rule out a leaking petcock as best as I can.
I'll clean these carbs, if I keep them they'll best be clean, and if I decide to go from a carb-set from the US I can probably sell them off easier if they're clean!