Fueling problem

[Auron]

Have an 07 with 19k. Probably had some bad gas but the problem has persisted through 1000 miles and my favorite fuel system cleaner.

Happens between 3500-4000 rpm in 5th when the engine is either lightly loaded or worse when hardly loaded at all. Constant throttle, the power cuts out by about 50%, loses about 5mph. If I don’t open the throttle to counter-act, it can take up to 10 second to recover the lost speed.

I figured out tonight that adding throttle very slowly does seem to set it off. This is all happening when the throttle is barely open. Bike runs great and mileage is very good.

 

[Larry Fine]

First guess: marginal spark plugs.

 

[Auron]

First guess: marginal spark plugs.

Thanks Larry. They were replaced at 11k according to maintenance records

 

[Larry Fine]

Thanks Larry. They were replaced at 11k according to maintenance records

Might be worth pulling them to check the color and condition, and reset the gap.

 

[Oldbikefixr]

Thanks Larry. They were replaced at 11k according to maintenance records

I grew up when spark plugs lived to the ripe old age of three thousand miles at best so I always check their condition whenever I change oil, along with the leads and caps. Unleaded gas has increased their useful period immensely. But.....an occasional plug will fail, sometimes without an obvious cause.

 

[Auron]

 

[Auron]

Gaps are good, air filter is new

 

[CYYJ]

Fuel Filter, perhaps? It's a PITA to change it on the 1300, but that's what I would look at. Remember that you will need a new big rubber seal for the top of the lower fuel tank if take the cover off to change the filter.

The other "possible" cause could be a blocked vent line running from the fuel tank to outside air. If you tilt the primary tank up, you will find three hoses under there. The far end (drain end) of the hoses sometimes gets blocked by road mud, or the hoses get kinked and that has the same effect. Perhaps check them to make sure there are no problems there.

Michael

Hose Connections under ST 1300 Primary Fuel Tank

 

[Andrew Shadow]

Start by checking to see if there are any fault codes stored.

 

[Auron]

Haven’t had the fi light come on…?
But it does look like this hose was smashed

 

[Auron]

Putting it back together, I don’t see how you can’t smash that hose if held properly with tie wrap thingy

 

[CYYJ]

Putting it back together, I don’t see how you can’t smash that hose if held properly with tie wrap thingy

Hi Auron:

It's actually really, really easy to squash one of the three hoses under the primary fuel tank. There is very little clearance under there, and unless the person doing the service pays very close attention to the service manual, it is easy to incorrectly route the hoses... thus leading to them getting squashed.

Here is a photo from the service manual (section 1) that shows hose routing under the tank. Be aware that everything can look great when the tank is up, but then something gets squashed when you lower the tank. I learned this lesson from the "school of hard knocks". To detect this, you can put a little talcum powder on the hoses, then lower the tank, then lift the tank and see if there is talcum powder on any frame members, etc. below the tank.

Michael

ST 1300 Under Fuel Tank Hose Routing

 

[Igofar]

Has anyone replaced the fuel pump with an after market one? Sounds like either your evap cannister hose out the bottom is clogged, one of your vent lines are pinched, or one of your fuel lines is damaged or loose, causing the bike to loose fuel pressure.

 

[Auron]

Pretty sure that pinched line is clear now, just rode it, no difference

 

[Auron]

Has anyone replaced the fuel pump with an after market one? Sounds like either your evap cannister hose out the bottom is clogged, one of your vent lines are pinched, or one of your fuel lines is damaged or loose, causing the bike to loose fuel pressure.

Pretty sure the fuel pump is stock. But I may have screwed something up with the canister when I installed my gear indicator. That possible?

 

[Auron]

Seems ok

 

[Auron]

I think my problem might be an aftermarket air filter. Emgo

 

[Igofar]

Air filter would not cause your issues.
Even K&N filters that cause the bike to run lean don’t do what your describing

 

[Chris09]

CYYJ posts a good pic from the manual of the underside of the tank; no small feat as far as I am concerned laying everything back in in the right place; easy to pinch / cross a line somewhere plus two other things I don't like; the factory built in interference with the ground stack and the fuel hose / set up between upper and lower tank I mean, [it's got pinto written all over it] what garbage. There's a couple sandwiches on this bike I really think are ____, and I haven't even ventured so far as lifting / disrupting the compliant fit between the bottom of the air box and the TB assy; I mean, don't get me wrong, out of the gate they're great bikes, but once they're dismantled and reassembled, Geronimo, who knows what you've got, unless... you did it yourself. But hey, it's all good jolly fun until someone loses an eyeball.

 

[Auron]

When I put the air box in, I can feel it click into the grooves. But when I put in the snorkel bases in, the bolts run out of threads (very clean and consistent) but the base isn’t actually secure. Like the bolts are too long.