Bogs down when opening throttle - first gen

[Irisheagle]

Hey guys,

Just to recap, 1984 Magna V45.

Sorry for the constant questions. I started my first adventure into rebuilding the carbs about two months ago with the help of a family friend who rebuilds primarily sport bikes. I had another post up here (http://www.magnaownersoftexas.com/forums/index.php?topic=4450.0) about a previous bogging down problem, and we ended up realizing we had lost a synchronization screw when getting into the carbs. We replaced that screw, and two broken/leaking fuel joint sets. Also replaced a broken throttle grip pipe.

Warp forward to now. No more leaking. Manually synced the carbs via synchronization screws so the throttle valves line up w/ the rear end up of bypass hole, although I haven't synced the carbs post installation into the bike. Checked the throttle linkage as best as I could prior to installing the carbs; the throttle valves all open up the same rate w/ each other and spring promptly back when I release the throttle pulley.

The bike is starting/idling really nice. However when I'm opening the throttle sharply, no matter what throttle range I'm in, the bike seriously bogs down. After releasing the throttle, the bike returns to idling really nice (previously before replacing the syncronization screw, the bike would continue to bog down after releasing the throttle). It seems if I roll the throttle open very slow and consistent the engine will spool up normally, though I can't be sure.

I'm still running 100 main jets and 40 pilots, and I'm still running the bike w/ the vacuum chamber open (no air filter, cover's off, etc.) Figure might as well leave all the extra stuff off if I'm going to have to pull the carbs off again.

I realized after the fact we had a spring left over, the "throttle shaft spring". Can't tell how important it is based off the diagram/pictures in the haynes manual, or if it might be contributing to this problem.

Any thoughts/suggestions are much appreciated. Found a guy that wants to trade his V65 for a V45, so trying to get this bike running as quickly as I can . I'll try and get a video of the issue posted on Tuesday, as I'm sure that might help you seasoned veterans.

Respectfully,
Dave

[dgc67]

still running the bike w/ the vacuum chamber open (no air filter, cover's off, etc.)

This will cause it to be lean.  Could be that it is so lean when you open the throttle fast it bogs due to lack of fuel.  Other thought is that diaphragms are not opening up as quickly as they should.  Just guessing here.

[John Luttrell]

I agree, the bike will not run right with the filter and air box open.

[Irisheagle]

Cool, I'll try doing that tomorrow and see how it helps.

[Irisheagle]

Fully installing the airbox resolved the majority of the issue. The only thing that's left is the bike is still bogging down slightly when jerking the throttle in the mid-throttle range, but after a second or two it picks back up to normal operation.

We tried further restricting the airflow through the airbox by covering half the intake with our hands, and this eliminated the problem, so we suspect it's still running a bit lean in the mid throttle range. Just to recap, main jet is 100 (stock 95), and we installed a brand new K&N filter. Could it possibly be the airbox isn't sealed completely, or perhaps we broke one of the vent joint sets when we took the carb out?

Kind of thinking of running the bike for a few weeks and see if the issue self resolves...

[John Luttrell]

deleted duplicate post..............

[John Luttrell]

I'd suggest installing a factory air filter to see if that corrects the lean condition; if that doesn't work, you will need to shim the needles to address the lean mixture.

[dgc67]

I'd suggest installing a factory air filter to see if that corrects the lean condition; if that doesn't work, you will need to shim the needles to address the lean mixture.

I agree, just to verify that is indeed the issue.  Remember that as the weather gets cooler the lean spot will get worse.  I added a K&N and went up one size in my pilots and moved the needle up.

[Irisheagle]

Will do. Haven't tried shimming the needles yet, but i'll try the air filter first like yall suggested.