Thinking it's an air/fuel issue, what do you think?

[nucleardon]

Hi all, I have had the 97 Tiger since February. When I went out to buy it, after a few minutes warm up with last seasons fuel, I took it down the road for a test. The PO had not bothered to add any stabilizer or keep the tank full, so when it hesitated at 2100rpm in 3rd, I just kept on going, eventually it straightened out. It was a bargaining point that allowed me to get the bike 400 cheaper, and had run great all through spring and summer.

In early September I jumped on to zip up the road for a small beer run, and noticed a "bog" and lack of power throttling up through second. Looked at the choke to make sure it was not on, check, so turned around and jumped on the Trophy instead. Last ride on the Tiger had been 3 weeks previous, a trip through the Trinity Alps with co-workers totaling about 250 miles, ran like a dream. So I thought maybe it was a fuel issue, added some Stabil, fired it up and let it idle a couple minutes, test run up the street, same thing.

Choke mechanism seems to be operating fine, (outside visual inspection), idle is steady, but when I crack the throttle I get the sense it's loaded up, and some popping/ backfire. So pulled the covers and tank, plugs are a bit black, like the mix is too rich (?). Changed plugs, but no difference. Fast forward a week, and more reading, I now have the breather box and carbs removed. I was going to pull out the filter and clean it, but there are two pair of #10 coarse thread screws on either side that won't seem to come out.

First question, how do the silly screws extract so I can clean the filter. And should I take a run at cleaning the carbs while they're off? I have read related postings where the thought was similar, " while the carbs are out, may as well clean them", followed by, " after reassembly it now runs worse than before"  .

PO had adjusted the valves, he has experience as a machinist so I feel they were done correctly. Rubber boots on both sides of the carbs are not cracked and seemed to be fitted well. All air box components are present and in the correct configuration, so my pea brain keeps coming back to carbs/ choke.

Thanks

[Sin_Tiger]

Looks like you have the later (I think) air box with two M5 screws rather than one self tapper. You'll have to take the carbs off to get the air box out anyway so you might as well give them a one over at the same time.

The M5 screws go into brass captive inserts,  so they have probably seized. Just pull them, then you can epoxy them back once you get them free.

[Mustang]

Last ride on the Tiger had been 3 weeks previous,  ..................

so my pea brain keeps coming back to carbs/ choke.

Thanks

3 weeks is enough time for things to go south with ethanol .
clean the carbs ...take them apart and clean 1 at a time , when you get everything all tidy put it back together , then do the next one , repeat for the third
nothing gets mixed up and if you get confused on reassembly you can still see how it goes together with one of the other carbs you haven't touched yet .

theres a sticky thread on how to clean the mikunis , they need it by the sounds of things

[nickjtc]

3 weeks is enough time for things to go south with ethanol

Yes; I speak from experience. Always stabilise the fuel if the bike is going to sit for any length of time.

[nucleardon]

Great, thanks for the input. Let you know how it goes. 

[rf9rider]

As Mustang said, clean the carbs thoroughly, pay special attention to the pilot screws, you need to use a strand of wire or similar to clean them out, don`t rely on just soaking them in cleaner or you`ll be chasing your tail.

[ssevy]

clean the carbs ...take them apart and clean 1 at a time , when you get everything all tidy put it back together , then do the next one , repeat for the third
nothing gets mixed up and if you get confused on reassembly you can still see how it goes together with one of the other carbs you haven't touched yet .

Doing them 1 at a time is a great tip! Never thought of that.

[nucleardon]

As Mustang said, clean the carbs thoroughly, pay special attention to the pilot screws, you need to use a strand of wire or similar to clean them out, don`t rely on just soaking them in cleaner or you`ll be chasing your tail.

Thanks, it's always the details that have you clinching in your sleep.

[nucleardon]

Soooo.... , no joy on fixing the problem by cleaning the carbs. They did need cleaning, two of the three had jelled residue and clogged pilots, now they are clean as a whistle. I refitted the airbox with the K&N that was in the box of spares that came with the bike. The filter in the box, once I managed to split it open, was literally caked with a dirt and oil melange' and was beyond cleaning. I also refreshed the pre-filter on the open side of the intake as it had all but disintegrated.
Tank back on, battery with a fresh trickle charge, and it fires up and idles like before, making a slight adjustment of the idle screw to no doubt compensate for the work I had done. I slowly advance the throttle after letting her warm a bit, and can get her to high revs, but with some smoke issuing out both pipes, followed by popping that seems to be prominent from the right can.
Deeper issue? I have a new fondness for my Trophy and her trouble free three years of riding joy,(crap, I just jinxed my self). .
Just a small synopsis, ran great on a long day ride, parked three weeks, issue with poor running and power loss surfaces, addressed carbs, air box, new plugs, fresh fuel and stabil added at the fill.
Thanks for any suggestions on which direction to go next

[ssevy]

I have rebuilt the carbs on my Legend, which are Keihins, and then the Mikunis on my Tiger. All I can say is Mr. Mikuni's brother must have owned an o-ring factory, as these carbs take a bunch of different sizes and are much more fiddly to put back together.
My point is that doing a thorough cleaning and rebuild is not difficult, but it does take care and patience. It would be easy to forget something or clean everything. The float needle adjustment, for example, is fiddly.

If you are confident that you did everything perfectly, and all of the float heights were in spec, then here is where I would next look, keeping in mind the holy trinity (air, fuel and spark):

1- Fuel: upstream at the petcock filters (I assume you cleaned the duckbill filter in the fuel line?). You didn't pinch the fuel line when you installed it? This is easy to do.

2- Air:  did a carb rubber get squished on either the intake manifold side or the air box side when you installed the air box? This is also easy to do. I run a stock air box myself, so I can't say if your K&N will mess up the air/fuel ratio enough to be an issue now that your carbs are adjusted correctly. Carbs out of synch can also make a bike run real ragged, and when you doing any work on the carbs, you should always re-synch after you are done.

3- Spark:  not likely, but could coincidentally have started just as your fuel problem was addressed. Plugs, coils, wires, etc.

2-

[t4tiger]

I'm having exactly the same problem and have tried the same remedies with no result.  I've also followed the advice on here and changed the jet size and put in the washers.  To my ears it runs beautifully when idling or gently revving it up but when under load it bogs down.

Could it be the coils? If so how would I check.  If not what?  many thanks in anticipation.   

[ynotbiker]

i live up in newcastle you could wip up and ill stick 3 coils on for you to test it.could be the way to go or you may have a fuel blockage check filters in tank.

[Sin_Tiger]

Did you check and/or remove the filter in the T between the carbs?

When you say fresh fuel, was the tank actually empty? Check the petcock strainers inside the tank. My personal preference is to ditch the tank and carb filters to fit a line filter after the petcock, either a replaceable or cleanable one.

If you didn't use a decent balance tool is unlikely you will even be close, triples are not easy.

[nickjtc]

Did you check and/or remove the filter in the T between the carbs?

When you say fresh fuel, was the tank actually empty? Check the petcock strainers inside the tank. My personal preference is to ditch the tank and carb filters to fit a line filter after the petcock, either a replaceable or cleanable one.

If you didn't use a decent balance tool is unlikely you will even be close, triples are not easy.

[t4tiger]

Thanks for the kind offer ynotbiker.  I may take you up on that if i can't solve this.  For now I'm going to check all the filters...anything but take the carbs out again...