Lately my 2008 GSf has been stalling on cold starts if I don't give it plenty of throttle for the first 5-10 seconds. It also backfires sometimes when I give it the throttle on start-up, and also during the first few minutes of riding. No problems whatsoever at higher speeds. This weekend I'm going to be doing my first round of maintenance work on the bike since buying it a few months ago w/ 10,000 miles on it (I know, a lot of miles for an '08, but I got a good price). I'm going to be checking valve clearances and cleaning the carburetors, and I just wanted to get some advice from the experienced members here as to what I should look for as I try to fix this issue.
From searching/reading all the relevant threads I can find, my guess is that the cause of my problem is either a clogged pilot jet or an air leak in the carburetors or intake manifold (an air leak seems more likely, as it would explain the backfiring). I crashed the bike a couple months ago at about 20mph, so maybe this could have caused a leak and/or clogged jet. Anything else I should check for?
One other thing. My mileage has been low since getting the bike (around 35 mpg, give or take--although I've only been doing city driving so far, no highways). So I also want to sync the carbs to see if this might improve mileage. I want to try the $5 diy carb-sync method, but the instructions in the wiki are a bit confusing. Could anyone point me towards a more detailed explanation, or give me a few tips for how to set this up? Otherwise I might just spring for a vacuum gauge. Anything else I could try that might improve mileage?
When my GS was running i found that two of the vacuum ports were uncovered on the carbs and gave the same start-up/cold running symptoms. But i have 07 carbs on a 93 with a non factory fuel petcock.
To eliminate things with your mileage, do you know what size sprockets you have?
At 4,000rpm in 4th you Should be doing close to 60kph / 37mph
At 5,000rpm in 6th you should be doing close to 100kph / 62mph
If this is about right with your bike you have stock sprockets and can now look into other areas for poor fuel economy. Let us know.
Michael
Thanks for the replies. Jeb, what/where exactly are the vacuum ports? I'll check them when I open up the carbs this weekend.
Mister, Those gear/speed ratios you mention are just about what I get on my Bike. I do a lot of cruising in 4th gear on the bigger streets, and I generally try to keep my rpms at 4000, which tends to get me in the high 30s mph. I don't ride as much in 6'th gear, but I'll be riding on the freeway tomorrow and will check my speed at 5000 rpms. But based on the numbers you list, my guess is that I have stock sprockets. I'll count the teeth tomorrow just to be sure. Assuming sprockets are stock, what else could cause mileage issues?
Running on one cylinder, perhaps.
When the bike is cold, start it up. Keep checking your exhaust headers for a temperature difference. If one takes longer to get hot, it's not getting spark or fuel.
Valve clearance going tight is my guess.
Cool.
Buddha.
Thanks for the tips. Paulcet, where exactly are the exhaust headers?
At 10k, valve clearances may be due for checking, I believe the interval is every 4k. I don't think your running on 1 cyl, you wouldn't be able to go up a hill or much over 7000rpm. You can just try warming up the bike for longer, and ride until the end of this season, and park it to do a valve shim change.
Quote from: paalak on May 24, 2011, 12:36:23 PM
Thanks for the tips. Paulcet, where exactly are the exhaust headers?
Those two pipes coming from the front of the motor.
I HIGHLY recommend that you get a service manual if you are going to do the work yourself.
Thanks again for all the tips. I think I've got the valve check and carb cleaning all figured out, but still wondering about the mileage issue. I'll be checking float height and trying to sync the carbs--anything else I should try? Also, I'm still not clear on how to set up the $5 DIY carb sync system. Is it as simple as connecting 2 long vinyl tubes to the carb drains and running the engine to check if the fuel rises to the same level in both?
Quote from: paalak on May 25, 2011, 04:43:08 PM
Thanks again for all the tips. I think I've got the valve check and carb cleaning all figured out, but still wondering about the mileage issue. I'll be checking float height and trying to sync the carbs--anything else I should try? Also, I'm still not clear on how to set up the $5 DIY carb sync system. Is it as simple as connecting 2 long vinyl tubes to the carb drains and running the engine to check if the fuel rises to the same level in both?
I did the $5 carb sync tool.It is as simple as it appears.I used the vacuum ports on top of the carbs.All you have to do is make sure the fluid level is the same in both tubes.Use the screw between the carbs to set it.I used red 2 stroke oil in case of a suck thru.I didn't because I bench sync'd my carbs before install.I just barely turned the screw to set them.
Thanks ben, that clears it up. I'll be syncing mine as soon as I finish adjusting my valves. I checked the clearances today, turned out the right exhaust valve is way under spec. My feeler gauge has a .02 blade, even that wouldn't fit. Other 3 valves are fine, no problem with carbs either :D
Quote from: paalak on May 26, 2011, 10:24:23 PM
Thanks ben, that clears it up. I'll be syncing mine as soon as I finish adjusting my valves. I checked the clearances today, turned out the right exhaust valve is way under spec. My feeler gauge has a .02 blade, even that wouldn't fit. Other 3 valves are fine, no problem with carbs either :D
Cool.I responded to your other thread.
if you can rotate the bucket with your finger you still have some clearance, then go down 1 size. if you can't then try 2-3 sizes.
Use a little more choke perhaps?
It's all good--changed from 270 to 265 shims on both exhaust valves, no more stalling issues :woohoo: