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Ignition (TCI) upgrades + some issues after winter storage

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Ignition (TCI) upgrades + some issues after winter storage

PostAuthor: kjt12345 » Fri Feb 09, 2018 1:26 am

Hello to everyone reading and thanks for giving your time,
I am not new to the forum, but am very new to posting so be patient with me as I learn the posting and response process please.

To make a long story as short as possible, I have been building a 1985 xv700 for quite some time now and have done alot of things to it. Fork swap from a CBR, single carb swap with new manifold, mosfet regulator, seat subframe for scrambler/cafe racer type of direction ive been moving (street scrambler?), many many modifications the the wiring harness for various things and fixing of alot of things...etc.. but it does have a stock exhaust, carb is mikuni vm38 with k&n pod filter, ran perfectly for all of last season (fighting regular fork swap issues and charging issues that led to regulator upgrade).

Now after taking the bike out of winter storage (has been started and warmed up plenty of times during winter (old oil, probably old fuel by now), I filled the tank with 91 octane from a jerry can and went for a short test ride in the 35 degree weather ( two block ride). The virago takes forever to warm up as usual, I leave the house and im getting random power loss when shifting, in turns, sometimes when accelerating. Stalls pulling into the gas station, then continues to have wierd bogging that I assumed was because I didnt let it warm up enough, I tuned the carbs in 80 degree weather last, and it had old oil in it.

Now this is where I have an issue, a block from home the bike wont go below 3k RPM. I hit the kill switch and get a backfire from the exhaust from the exhaust that sounded like a gunshot. I stood on the road and started/shut down the bike about 3X and it continued to high idle and backfire on shutdown. I walked it home and after restarting it a few more times it went back to normal. The only time I have had high idle was when the main carb needle would get stuck when I first started building. I have no idea what to make of this.

I am interested in upgrading my a TCI (Speaking with Ignitech) before I tackle exhaust, i can only imagine this being a gummed up carb issue or an engine electronic issue at its one of the only original parts on the bike. Any feedback is appreciatted,looking to smooth this out before I start changing any parts

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Re: Ignition (TCI) upgrades + some issues after winter stora

PostAuthor: sequim » Mon Feb 12, 2018 11:19 am

I'd start with clean fuel and carb cleaning. Good luck.
The members of this group helped me with the most difficult challenges I faced in building my own Bobber... Thanks Virago Tech Forum.
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Re: Ignition (TCI) upgrades + some issues after winter stora

PostAuthor: faffi » Thu Feb 22, 2018 3:53 am

Before you replace anything, it pays to work methodically. Follow your own routine, but this is what I personally would do:

1. Hook up a strobe timing light and check for regular spark on both cylinders. The strobe will only flash if you actually have a spark inside the cylinder when the engine is running.

If spark is reliable, I would also time it. AFAIK, you can only time the rear cylinder, but that should be sufficient.

If both timing and regularity is fine, then the issue is quite likely to be fuel related. Either you have a leak allowing false air to enter (quite likely since revs are hanging) or something in the carbs have clogged during storage. It could be other things as well, like poor flow from the tank, but these are less likely in my experience from the symptoms.

If spark is unreliable, it doesn't have to be anything wrong with the TCI. It could be something simple like a loose battery connection or a poor contact on the sidestand switch. It could also be a bad spark plug or a bad coil. Or even a cracked spark plug cap.

Going meticulously over the bike, inspecting wires and connectors, spraying around the carb and inlets with starter fluid when the engine is running and listening for changes in rpm, checking valve clearances etc. is in my experience the safest way to find the culprit. And also cheaper than just throwing parts at it. You may learn that you need a new part, but at least that is then based on knowledge, not desperation :bg:
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Re: Ignition (TCI) upgrades + some issues after winter stora

PostAuthor: kjt12345 » Thu Feb 22, 2018 10:50 am

Faffi- damn you are good at this lol, so i started with checking for air leaks since i had starting fluid nearby... so 1.found an intake leak :ops: .... 2. continued to check fuel lines and flow because that was 2nd least invasive... petcock was being kind of wierd and ended up getting my carb to pour out of the overflow, so I i probably have some gunk in there hanging up my floats and probably other things also.

So I guess i have my work cut out for me, ill patch that intake, take apart the carbs, and check the petcock and come back and let you know how it goess, looks like a mixture of those things is the cause though. Thanks for giving feedback, much appreciated, less time tinkering is more time riding :bg: :bg:

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Re: Ignition (TCI) upgrades + some issues after winter stora

PostAuthor: faffi » Thu Feb 22, 2018 5:22 pm

Glad that I could be of assistance :cl:
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Re: Ignition (TCI) upgrades + some issues after winter stora

PostAuthor: kjt12345 » Tue Feb 27, 2018 10:46 pm

Update- I think ive gotten to the bottom of this set of problems. Did all the things I said in the previous reply in terms of things to check. I found a few different things and cleaned them all up
1. Some moisture in the bottom of the carb bowl, found this when I removed the carb to clean it, looked like about a shot glass worth of water in my fuel
2. Adjusted the petcock and cleaned it some more ( bent the washer inside as it doesnt use the original vacuum mechanism anymore)
3.Installed new TCI/ECU however you prefer to call it, made a huge improvement in alot of areas (will make a post describing the process and benefits of the new unit)
4.Cleaned the carb really good :blah: :pee:
5. New plugs (NGK 7131) and lucas upper cylinder lube for good measure
6. LUBED NEW THROTTLE CABLE, TRIMMED CABLE END ( This is what was actually causing my hanging throttle. cable end was shifting around inside the carb, and holding up the slide after moving a certain way. Took a file to it so it wasnt so obnoxiously large)

Fired right up, No more hanging throttle, no more backfiring. Went for a test ride, felt like a brand new bike with all the new parts. Now I think I might need to change my timing on my new ignition, or a little different main jet as I got some popping through the intake when doing a launch from a red light. But that is something separate for a different post :thanks: :thanks: :thanks: for the help

I keep putting such detailed posts in hopes that someone will be reading this trying to troubleshoot and wont be missing any info from how i resolved my issues. Hopefully some of you guys can benefit from my note keeping on the build and all of its many many little issues

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Re: Ignition (TCI) upgrades + some issues after winter stora

PostAuthor: faffi » Wed Feb 28, 2018 5:15 am

:GJ:
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