Chasing some midrange on a 00' Sabre

[damian.garcia83]

Hey gents,

I am getting frustrated to the point of giving up and turning it over to an indy shop so here goes.

My low end and top end power on the Sabre is excellent and showing great plug readings when run at the correct throttle applications. However, whenever I run in the 30-80% throttle opening range, it seems like I am just dying on power (feels like the engine just flatlines with static torque/hp) and getting erratic plug readings when doing the throttle chop. Sometimes it reads lean, sometimes rich even when I have not touched the carbs.

I have verified all the rubber hoses and I can't seem to find a vacuum leak anywhere. Do you guys have an idea of what I may be overlooking here? When I first got the bike, I cleaned both carbs extremely well and with great detail. This included breaking down the air circuits on the sides of both carbs and all passages, jets, etc. Also, all parts are stock minus the main and pilot jets (178, 182 mains and 45 pilots to accommodate mods). I have verified and reverified the float height using the correct method/tool as well and both are spot on. The airbox is clean and clear along with the air filter. Everything is as tight as need be and hence why I am stuck.

Help??

Damian

[Dom.Five]

Sounds like a clogged or restricted high speed jet.

[93gc40]

I am assuming the slide is moving freely. Your mid range is controled mostly by the NEEDLE. Try raising or lowering the needle, via shims or if DJ jet kit, change groove. Raising the needle richens. I would also suggest going smaller on the pilots jet. BUT I DON"T WANT TO ARGUE ABOUT IT. Are you running staggered mains for a AF mix reason. IS the rear cyl. really running hotter than the front? Have the carbs been sinc'd? Are you 100% sure there are no leaks or restictions in the vac hoses or intake boots or diaphrams?

[gat803]

I agree, you might be looking at needle mods....perhaps the most difficult part of carb tuning to get right.

[damian.garcia83]

Originally Posted by Dom.Five

Sounds like a clogged or restricted high speed jet.

Which is the high speed jet? Main or pilot?

Damian

[damian.garcia83]

Originally Posted by 93gc40

I am assuming the slide is moving freely. Your mid range is controled mostly by the NEEDLE. Try raising or lowering the needle, via shims or if DJ jet kit, change groove. Raising the needle richens. I would also suggest going smaller on the pilots jet. BUT I DON"T WANT TO ARGUE ABOUT IT. Are you running staggered mains for a AF mix reason. IS the rear cyl. really running hotter than the front? Have the carbs been sinc'd? Are you 100% sure there are no leaks or restictions in the vac hoses or intake boots or diaphrams?

Yes, the slide is moving freely. It doesn't matter if I shim or don't shim the needle I am still getting the mid range stumble/flat line.

And I won't argue regarding the pilot jets, I moved up because I ran out of adjustment doing the idle drop procedure to set the pilot screws and had to move up.

Last time I did a IR thermometer the rear was running around 10 degrees hotter on average to the front cylinder. I have always thought that it was just due to the packaging of a V-twin that it would be the cause. Even the OEM jetting is 175 front/180 rear.

I am in the process of attaining a manometer for carb sync purposes, but the carbs have never been separated so this wasn't high on the list of priorities.

Now, here's the good news. Realizing there was only really one external vacuum line (the top cross vacuum line between the carbs that runs to the rear of the frame), I checked that for flow and did not get any. I followed the hose down and realized it was getting pinched where the exhaust heat shield is on the frame. Once I relocated that, I was able to get air flow through there. Do you guys know where this runs to on the bike? (00 Sabre) I couldn't track it down past behind the exhaust heat shield to check the whole line for pinches.

I haven't been able to test ride the bike - might be able to later on. And I will let you guys know if that helped the situation.

Damian

[damian.garcia83]

So in the test ride, the bike is kind of acting like it has a turbo set up, well sort of. I have strong low-rpm, low throttle opening response, but then a flat mid range, followed by a storm of power on the high rpm, WOT load.

I am still trying to chase that one vacuum line and can't find a vacuum diagram for it in the manual. I am also going to be sync'ing the carbs this week and hopefully between those I can resolve the problem. Any other inputs would be appreciated.

Damian

[damian.garcia83]

First off, thank you so much to all of you for your help and suggestions. A new member who hadn't done his three posts even went so far as to send me a pm on this matter. Thanks cyclejohn!

However, the problem did not lay in the bike, carbs, jettings, motor, or anything else that has to do with anything but the nut who was turning the wrenches...

Apparently, I was putting the carb diaphragms in incorrectly by not holding them in the up position while putting the top cover on. This apparently was leading to the erratic plug readings (rich/lean) and my horrible loss of midrange power. So now that I reinstalled them correctly, I went back to my dyno's jetting settings and the bike was awesome again.

Funny, I now remember what a bike is supposed to feel like and not by having to get on my sportbike with its wonderful fuel injection and high hp/low weight!

Damian