Slow top end......

[brcree]

Well.....the monster is back together and have been able to take her out a few times now. It doesn't seem to want to go any faster than about 50 or so??????? starved for gas?....no octy....inline fuel filters...stock jets.....carbs have beencleaned and syncd. Any thoughts?

[DGXSER]

How did it run before you made changes....what changes did you make if any? Have you verified the fuel lines are not pinched anywhere?

[brcree]

top end

Hey DG, good to see you again....well this bike was a barn find ( snotter)......hadn't ran since 85. Good compression.......and have had to do the dremel 2nd gear fix....so PO must have dogged it! Haven't made any changes from stock. I have the fuel lines passing over the boots going to the airbox...I don't like it and thought maybe passing them under the boots...what do you think?

[DGXSER]

Well, there are plenty of folks who run the fuel lines like that with great success. For me, every time I tired it I had one line or another kink up or air lock on me.

I do not use the Octy, I hook the fuel lines to the ON port of the petcock, and straight down between the 1-2 or 3-4 airbox inlets. I put the pyramid shaped in-line fuel filters on, they fit between the inlets. I run the left side petcock to the 1-2 carb inlet, and the right side petcock to the 3-4 carb inlet. Most direct route. I do leave enough fuel line between the filter and the carb so it loops down and almost touches the engine case. Leaves plenty or room for lifting the tank up to remove the lines.

Now, this is like asking what oil to use, there are many ways to run the lines, and every one has their favorite. This is what I have found works best for me.

Since you have no history on this bikes performance, fill us in on a few more details. What year bike, what year/style carbs, POD or airbox, stock or aftermarket exhaust, 4-2 or 4-1? Does it run smooth and poerful in the low end, and then just run out of steam at the top end? Is it at a certain RPM no matter what gear you lose power?

[IanDMacDonald]

My first thought was air/fuel issue, but, that could be a little ignorant. What kind of airbox are u running? Stock or pods? If ur running crap pods, maybe an airpassage in the bell is being blocked?

Vacuum advance?
Plug color?
Mufflers blocked?
Full power in lower gears?

Just a few of the many thoughts in my head. If you look back a year or two, I actually have a thread on here that I hi-jacked from another member regarding this issue on my XS750. Ended up being cheap pod filters.

[brcree]

Top end

The year......81 S H model
Carbs have the recessed Air/Fuel needles.
Stock air box
Stock Pipes.
It feels good going up through the first 4 gears...and seem to peter out in 5th. I rev it up to around 4 grand between the shifts. I'm going to try your fuel line routing.......I have the pyramid type filters as well....and yes they are installed correctly....ha ha. It just seems like this bike should be parting my hair by the time I get in top gear. Good stuff Ean......that was my next thought on the vac advance......what can be checked on this system? Ean....do you remember the title of that posting from way back?

[bikerphil]

It's the mechanical advance that can give you power issues, not so much the vacuum advance, vac. advance is mostly for fuel economy. The 81 models use an electronically controlled timing advance which is controlled thru the TCI which should be a 4R0 type. There should be no mechanical advance weights behind the timing plate for this system. All the earlier systems (78-80) used regular mechanical advance (spring & weights mechanism) behind the timing plate paired with the 2H7 TCI box which has no advance mechanism built in. I would check your system and see if you have mismatched components which would fail to properly advance the timing, causing loss of power. When you finally do get it running right you better be holding on tight bro.

[brcree]

Thanks Phil: so you are saying the 4ro TCI box shouldn't have anything behind the timing plate..correct....and the 2h7 box will?

[bikerphil]

Thanks Phil: so you are saying the 4ro TCI box shouldn't have anything behind the timing plate..correct....and the 2h7 box will?

Correct, which TCI are you running?

[motoman]

Thanks Phil: so you are saying the 4ro TCI box shouldn't have anything behind the timing plate..correct....and the 2h7 box will?

Yes and no, example when I got my Venturer back it had a 2H7 TCI. Wasn't correct, but ran....after a fashion. In other words, TCI type doesn't necessarily conform to advance type. PO's can end up with who knows what. 81 only used the 4RO TCI. So, what TCI lurks under the seat?

[IanDMacDonald]

http://www.xs11.com/forum/showthread.php?t=30214

[TopCatGr58]

The year......81 S H model
Carbs have the recessed Air/Fuel needles.
Stock air box
Stock Pipes.
It feels good going up through the first 4 gears...and seem to peter out in 5th. I rev it up to around 4 grand between the shifts.

You're barely getting it out of IDLE rpm, can it actually REV up to 7500 or so in any gear??? If it won't rev much more than 4k, then I would suspect what the others have stated, you probably have a mismatched TCI... someone being told their OEM was burned or mess up, and put a 2H7 series in it instead of the 4Ro, and that will NOT run very fast or strong because of no cent. adv. action !

The 4RO TCI's were only made for 1 year, and are often rather pricey because of that. Some folks have taken the mech. adv. parts from an earlier model and put it on their later machine so that they could use the earlier style TCI!

T.C.

[brcree]

top end

Will be taking a gander under the seat today...will report back!

[brcree]

Top end..............

OK...here it is: TCI Box is a 4RO-10....looked under left eng. cover and don't see the mech. adv. bits...just a couple of black plastic covers (pick-ups) I'm guessing.

[GLoweVA]

Just a thought, back in the summer of 2011, one of my pick up coil wires opened up on me. (didn't know that was it at the time) and I had to limp it home from work.
Basically, it was running on 2 cylinders the whole ride on the interstate.
I could barely maintain 55MPH at WOT. It was really slow to accelerate.
I ended up burning a hole in #3 piston.
Anyway, I bring this up in case you might have a pick up coil issue.

It could also be drawing a vacuum on the tank with the larger demand of fuel at the higher speed/load, try poping the lid off the tank and see it the problem is still there.