Ignition and vacuuum advance problem.

[lonestarmedic]

How much increase in RPM will a vacuum advance provide?

 

Can an ignition box advance enough to run a bike at 3000 RPM?

 

Have been chasing strange problems on my 1986. Thought it was all carburetor related. Went through with a fine tooth comb about 6 times. Idle has been erratic and throttle seemed to hang and be slow to return to idle. Warmed up bike to check some adjustments. As I was listening to idle after adjusting mixture the bike revved to 3000 rpm without being touched. Blipped throttle and pushed on linkage. All seemed good.

 

This did NOT happen until bike was good and hot. Running on centerstand for 20 minutes or so.

 

Pulled hose for vacuum advance off of the carb and idle dropped down to about 800. Plugged in and up to 3000! Capped off the carb and left vacuum unplugged. Revs up great. Almost too good for no advance. Like ignition box has a problem. Put a Mityvac on advance. Pulled a tiny bit of vacuum and bang up to 3000. Amount of vacuum pulled did not even move needle on gauge. Talking imperceptible. Grabbed a spare vacuum advance and plugged in. Same 3000 rpm. Have NOT bench checked the vacuum units yet. Both are 30 years old. I also have an untested 41R CDI box from a 1986 parts bike. Looks good but who knows?

 

Tomorrows project is test the advance units and clean up ignition box and swap it out. Also compare engine amd electronics hot versus cold. Maybe CDI gets good and hot and goes haywire. I had the box off the bike earlier this year. So hardware will not be a problem.

 

This is a real puzzle. A screwed up ignition would sure explain the low vacuum on the Carbtune. And bike was running ok 2 weeks ago. So this is possibly something that has been going bad and just went flop right in front of me.

 

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[MasterGuns]

I'd replace the cdi and recheck. Mount the cdi atop the air box so changing it out only takes about 60 seconds.

[frankd]

On my 89, the vacuum advance is locked out (by the tci) until the engine is revved up somewhat. If I apply vacuum to the vacuum advance line with my mighty-vac with the engine idling, nothing happens. If I have somebody hold the throttle and keep the bike @ 3000 RPM with no vacuum applied, when I apply vacuum the engine speeds up considerably. It appears that your TCI has a problem.

[lonestarmedic]

Thanks franfd-

 

That is what I though. Vacuum advance should not hit until at least 1500 RPM. So I suspect I have found my culprit. Too bad I spent all the time and money on carburetor restoration. Ah no, the carbs were all original so they needed it too

 

JB

[lonestarmedic]

I'd replace the cdi and recheck. Mount the cdi atop the air box so changing it out only takes about 60 seconds.

 

 

No room up there on mine. I put the replacement fuse panel on the box. But, I agree it sure smell like a CDI box problem.

[MasterGuns]

No room up there on mine. I put the replacement fuse panel on the box. But, I agree it sure smell like a CDI box problem.

 

PM sent

[lonestarmedic]

Vacuum units are right on the money. Used TCI is scrap. Tach needle bounce. Ignitech on the way from a friend who bought one and decided not to use it.

[lonestarmedic]

Update on project.

 

Installed Ignitech unit and fired bike up. Ran ok but found the right front cylinder was not running right. Pulled plug wire and no RPM drop at all. Other cylinders caused quite a drop. Decided to bite the bullet and drop the coil rack out and test it. Everything right on the money on the bench at 3.7-3.9 Ohms and 13.7K-13.9K Ohms. Physically the coils look good. Plug wires and caps also right on the money reading 4.9K Ohms. Tested pick up coils and they showed 120 Ohms. Ran through the harness and connectors. All seem clean and tight.

 

So, going to install the Ignitech unit and convert over to Coil On Plug just to be sure. Any of these 30 year old items could be failing when hot. Put the whole mess back together and set the Ignitech for the COPs. If this does not solve my weird running problems then I will either send the carbs off to DannyMax for a checkover or run the bike into the pond!!

[frankd]

Does the right-front cylinder run on the original TCI? Are you certain that the Ignitech is setup correctly? A year ago my 89's TCI started to get a bit flakey after I washed the bike. I got all paranoid about it leaving me stranded while we were on the road, so I purchased a new Ignitech kit. Mine arrived setup for a VMax. I tried the program for the 83-89 Ventures that was on the CD in the kit, but with it the engine would be hard to start-hot or cold. You could tell that the timing was advanced a lot because even with heavy duty battery cables, a relatively new AGM battery, and a 4 pole (aka 4 brush) starter, it would barely crank and you could hear the engine fighting the starter. With the program I selected the option to not provide spark until the engine cranked over a couple of times and the hard starting was cured, except the bike always had to crank for a bit before it started. Then I noticed that my mileage was down bit compared to the OEM TCI and the bike felt and sounded different when I was riding at a steady speed. I disconnected the vacuum hose to the new MAP sensor. It only had a small effect, as compared to the OEM TCI. We were leaving on a trip so I re-connected the OEM TCI. I intended to remap the advance curve, but I haven't gotten to it yet. I've got the Ignitech mounted to my air box so it's ready in case I need it. I figure all I'll have to do is to pull the battery and battery box and reach down and get the plugs for the TCI and bring them up to the Ignitech. I'd also have to connect the vacuum hose for the new MAP sensor. Better than being stranded in Podunck.

 

Make sure you have correctly timed spark for that dead cylinder before you pull the carbs. If there is any chance that moisture has collected in your spare TCI, put it in the sun and dry it out and try it again.

[lonestarmedic]

frankd -

I think I had spark to the now dead cylinder with the original TCI. Been enough done that I am starting to blur a bit.

The second TCI has a positive cylinder 2 tachometer drop.

Both have been dried thoroughly. Neither were wet for months before that. No bike washing or rain.

I believe this Ignitech is set up with a Vmax program. However it did start easily.

The MAP sensor is good for about 4-500 RPM.

 

I did find a problem with the Ignitech wiring. A WIRE TO THE PICKUP CONNECTION FELL OUT OF THE IGNITECH SIDE!!!

 

Now, I am so far into everything that I have the coils on the workbench on their rack. So re-assembly needs to happen so I can see if that wire was doing anything or not. It may have been making contact. It darn sure is now. I pulled the connector apart and soldered the crimps.

 

I mounted my Ignitech unit on a heat-shielded and modified coil rack. The unit slid right between the coil mounting ears. MAP sensor is right next to it. The programming port can be accessed from the front right side of the fairing. Reach up behind the fork and it is right there. And will have a plug over it so it does not get wet.

 

Waiting on my COP units and wires to arrive. Then will splice those in and see what happens. I have faith in the new Ignition, I do not trust my old units. It is possible I need to remap the box slightly to match the Venture cams as opposed to the Vmax.

 

Will make sure I have good spark to all cylinders befor I pull carb bank off again.

 

JB

[lonestarmedic]

Ok, most of problem solved. New thread on ignition started.