Can't seem to quite get the timing dialed

[pnedac]

Well I finally got the bike up and running, but not without some trouble of course. I can seem to get the timing to relax. I am running a SPARX and a Boyer Branson ignition and it starts and I ken get the idle to be okay, but as soon as I hit the throttle it jumps way higher in RPM and won't come back down unless I retard the timing, but then I am retarding the timing past where to needs to be and it'll die. Reset it and it fires right up. Then I get it dialed in and then I hit the throttle and it jumps up. Vicious cycle I am caught in here. Anyone have a suggestion on something I might be missing. I have ridden it and it will idle too high until I put it into gear and then it seems cool until of course I go back to neutral. Same vicious cycle. I am officially confused. Cam Chain set, valves set, white paint dot lined up behind the magnetic advance and engine at TDC. I am missing something? These are also brand new carbs professionally set up by MMM at 650 Central so I am trying to stay away from jumping into them if at all possible. Could be there too though.

Any help is appreciated.

 

[TwoManyXS1Bs]

I presume you have VM-34's?
How many turns are on your idle stop screws, between where they are now and with the slide(s) fully bottomed?

 

[pnedac]

Correct on the VM34s. So they started out at 3/4 turns out, but I was messing with them more yesterday and did manage to get it to behave better. Not perfect, but better. I think on Thursday I will do the synching of the vacuum and at that time I will get a little assistance in getting the bike truly dialed in. I think it will be a matter of getting the idle dialed on the carbs once. Good looking out on the help. I think it will be okay. It always turns out well in the end.

Cheers!

I presume you have VM-34's?
How many turns are on your idle stop screws, between where they are now and with the slide(s) fully bottomed?

 

[Brian902]

Had VM34's on my XS650SE engine and was running 1 1/2 turns on the AIR mixture screws.

The AIR jet in the intake throat was removed by me as suggested by others here on this site.

The throttle stop screws, the ones that control the slide stopping point, are you idle speed and need to be equal and best done using something like a set of vacuum gauges. But a good ear can detect the difference in exhaust and rpm as you adjust on one and then the other. I'm not that good, so use the gauges.

Any air leaks will give you fits. so make sure the caps are good on the vacuum ports if the intakes have them.

Good luck.

 

[pnedac]

Had VM34's on my XS650SE engine and was running 1 1/2 turns on the AIR mixture screws.

The AIR jet in the intake throat was removed by me as suggested by others here on this site.

The throttle stop screws, the ones that control the slide stopping point, are you idle speed and need to be equal and best done using something like a set of vacuum gauges. But a good ear can detect the difference in exhaust and rpm as you adjust on one and then the other. I'm not that good, so use the gauges.

Any air leaks will give you fits. so make sure the caps are good on the vacuum ports if the intakes have them.

Good luck.

Good looking out. What is the purpose/logic behind removing this intake throat? You get better performance? I will also check that the vacuum barb covers/plugs are snug. Everything else is new so shoudl not be any air leaks. I could see if I were trying to get away with using the old cracked boots, but those have been replaced as well. I will look into the throat thing.

Cheers!

 

[Brian902]

Not the intake throat, the Air Jet in the intake throat.

It helps to lean out the idle/low speed range of the jetting, by allowing more air into the circuit.

 

[pnedac]

Gotcha. I wil look into that first thing this evening. How far do I need to take the carbs apart to remove it? I will look in the Mikuni manual at any rate, but just curious if I can pop the carbs off and get to it easily or if I need to take them out, take the cables out, take the things all the way apart to get to said air jet. I appreciate it for sure. That is a great place to start looking.

cheers!

 

[pnedac]

Disregard. I can see it. It looks like I just need to pop off the carbs and take it out. Looks like a simple thing to check. Thanks again!

 

[Brian902]

Hope we are talking about a set of these. One of your pictures show original looking carbs.

And if MMM did the setup, these could already have been removed.

 

[pnedac]

We are on the same page and yes, MMM may well have taken them out already, but never hurts to check. This is my 4th XS so I am sure I have different pictures floating about. I have used the stock carbs in the past if they were in good shape and could be salvaged, but in some cases (such as this) I think I should just pay a little extra for the long term rather than go through all the hassle of rebuilding the originals.