tci box

looking at chacals diagrams. it looks to me like all the tci box does is act as a switch for killing the motor. via kill switch, ignition switch. am i wrong? does the tci control the spark somehow also? (such as the timing).

my bike feels like it's missing on low rpms. under 4k. so i'm wondering if it's not a timing issue. between 4k and 6k she runs like a champ. around town. sitting at a stand still it'll run to 8k or above and then surges.

so i'm wondering if my timing is advanced at the low rpms. at 4k she's perfect. since timing is non adjustable. there has to be some electronic device that controls the timing. and isn't setting it back at the low rpms. and possibly not advancing enough at the high range. the bike idles good. but any throttle acceleration is missfiring untill it hits that 4k sweet spot.

and my gas mileage is very poor. about 100 miles to the tank.

 

The timing is not adjustable on the XJs. The TCI gets its input from the pickup coils, and automatically changes the ignition timing based on engine RPM.

Low-RPM miss could be fuel-related. See if it improves or gets substantially worse if you add a bit of choke lever while you're riding. It could be caused by a vacuum leak, a hole in one of the diaphragms, low fuel level, or some other problem causing a mixture imbalance.

It could also be caused by lack of juice... XJs love those fully charged batteries, and they don't make their own juice until you hit about 2500-3000 RPM.

Another possible problem is weak ignition coils or faulty pickups, but if it runs OK at high RPMs, the pickups are probably fine.

What kind of bike do you have, and what all has been done to it?... Carb work? Pod filters? Open exhaust?

 

+1 on the juice, excellent point

 

charging system starts at battery voltage and climbs to 14.5 volts as the throttle is revved. max volts hitting at 3000 rpms.

carbs have been checked and rechecked and rerechecked. ALL jets are the right size and in there proper holes. floats have been set at 18mm, 16mm, and 14mm.

all vacuum leaks have been fixed. including new intake gaskets.

coils tested 11.5k ohms.

new plug caps. new plugs.

compression checks at 140 lbs. i now have no difference on different cylinder kill tests. disconnect ANY cylinder and i get the same performance effect on 3 running cylinders. so there all firing.

everything that could possibly be wrong has been fixed. so, the only issue left is timing. and if the TCI is what changes the timing. then that's got to be my problem. it's not resetting back at the lower rpms.

it's also got to be why i'm only getting 100 miles on a tank instead of the 180 miles i was getting when i had this exact model back in high school.

i've either got a timing issue with spark, OR valves. but since the bike runs like a champ at 4k rpms. i'm inclined to go with spark timing. it also struggles at about 65mph. on a straight freeway road i can hit 75 but a slight climb brings it down.

specs call for 10 degrees or something at idle. 35 degrees right around 4k and 37 degrees maxed out. i haven't verified with a timing light yet. but i'm starting to beleive that timing is running at 35 degrees advance on the lower rpm scale.

if ridden for awhile, the bike DOES smooth itself out so that lower rpms actually work. down to 2500. but never lower. and even at 2500. it's still not as crisp as it should be.

there is a motorcycle boneyard that sells ANY part for $20. with any luck he has a replacement i can try. if it don't work then i'm only out $20. and the issues has to be valve timing or adjustment.

if there's any other suggestions. i'm all ears. cuz i'm clueless as to what else might be wrong. all the basics have been checked and fixed.

i haven't tested the pick ups yet. but according to the book. they either work or they don't. and i've pulled all 4 plugs and cranked the motor over. i'm getting fat whittish blue sparks on all 4 plugs.

 

There's an easy way to check the timing on each cyl.
After warm-up and 1 min at idle, pull each plug and check
the ground strap. there should be a change in color somewhere
between the top and the bottom.
If timing is perfect the change will occur in the bend.
Two of my cyl are on the money and two are closer to the threaded
end.
Of cource with a fixed timing the only op's are pick-up coils,
ignition coils,TCI,wires and plugs.

 

snowwy, I now have the same exact problem as you. I'm going to do the charging system check w/ my V meter in a few hours. Put all my stuff back together this morning and now it's the same as you. it's got NO BALLS when I take off & chattery, terrible under load till 3500 or so

about the junkyard parts, TCI's are super vulorable to moisture, being outside, I wouldn't consider that a good source for that particular part. especially since the side cover probably isn't there which leaves it dirrecty in the rain, bad bad bad

 

if your vacume is low, I guess it wouldn't open the petcock enough for a good flow. So turning it to Prime while riding should be an instant trouble shooting method right?

 

the fuel switch is working just fine. either in the on position or prime makes no difference.

as for the boneyard parts. he has a crate of ignitor boxes sitting on a shelf inside the shop. and he just happens to have 4 for me. he's going to let me take the bike down and try one first before buying. as he wants $100 for one.

 

I'll reiterate what Steromind asked, what year and model are we looking at?
When you say you have fixed all of the vacuum leaks, how are you sure? Did you replace the carb shaft seals as well?
I do not suspect your TCI, they either work or don't work. I've not run into one that works part way.
Please respond with requested data.

 

it's an 81 xj650. there is aboslutley no vacuumn leak whatsoever. ABSOLUTELY NOTHING happens when using the propane enrichment method. so nothing is sucking in air.

the tci is what controls the timing. at least that's what everyone says that i've talked too. so, just becuase it works don't mean it's working 100 percent.

if the tci doesn't control the timing then what does. the pickups are permanently mounted. there's no mechanical advancing plates. the coils and plugs don't control the timing.

since the bike runs like a champ above 4k. but max rev is about 9000 if lucky. mostly it's 8000. max freeway speed is 70. 75 if the road is straight and no gusty winds.

so i'm thinking the timing is stuck at a certain spot. at 4000 rpms timing is perfect. but not advancing any farther for the higher rpms. and not setting itself back at the lower rpms. 4000 to 6000 the bike runs like a champ.

timing calls for 12 degrees at idle. 35 at 4000 rpm. and 37 fully advanced at 6000 plus. so i don't think the spark timing is working.

this isn't my first rodeo working on bikes. and i was a car mechanic for 12 years. so I SAY ALL THE BASICS ARE COVERED and anything that was wrong has been fixed. whatever my problem is. it's pretty sophisticated and not some basic crap.

 

I think the entire advance curve is programmed into an integrated circuit "chip", and either the entire chip "works" or it doesn't............Robert, isn't that the way that those little critters usually perform (or don't)?

 

well, apparently the chip isn't working as far as the timing goes.

i went to the boneyard and tried a different tci. the bike wouldn't idle. BUT, IT RAN LIKE A CHAMP.

which means the timing on my tci is stuck in advanced mode. it idles with advanced timing on the old box becuase the bike is adjusted for a malfunctioning ignitor. but not with SET timing on a properly functioning box. gonna have to readjust once i get the money to buy the part.


ANYWAYS. MY DILLEMA IS SOLVED. as soon as i can buy the part. AND I JUST WANT TO SAY THANKS FOR EVERYONES HELP ON INPUT AND SUGGESTIONS.

by the way. the bike is really running like crap today. so i probably won't be riding it untill i get that part. ROFL

 

Looks like we both got it on the same day man. Its not over till We Own the Working Parts and have Reliable bikes. I'm done celebrating early. But I will for you. Congrads

 

snowwy66:

I don't know, snow-man ... It seems like you already popped "The Bubbly" and shot-off all the confetti favors before conducting Real World Testing.

The Odds that your TCI was bad, getting stuck, and not advancing the spark are: Az--tro--nom--uh-cull.

You got a better chance of winning Horse-racings Triple Crown.

Not you betting and winning.
YOU actually running and winning!

But, we all eagerly await to hear what happens when you plug-in the Un-cursed TCI and try it.

 

LOL.

already tried it, and drove it. left the seat at the yard so the guy know i would be back. and i drove it 3 miles. BIG world of difference. didn't even recognize the bike.

i'll probably just break out the visa and pick it up after work. expensive, but there's only 2 i can find. they both are on ebay and want the same money.

 

First time I've heard of a partial failure of a TCI.
I must say I'm curious as to what went bad on your TCI. I do have a spare TCI for your year and displacement should the need arise... (and I do want to look at yours, professional curiosity you understand).
I offer a TCI refresh for a whopping $25. New electrolytic caps and any other solid state parts it might need (if they prove to be bad). I isolate and test all transistors and diodes while I'm at it. I CANNOT repair a bad timing chip, once they go, that's it, its a doorstop. You might drop me a line perchance...

 

chacal made a mention of wrong resistance overworking the tci. don't know how true it would be. but i won't doubt it either.

with one cap being 185k ohms. measured on the 200k scale. and previous owner had porsche spark plugs. (don't know the resistance factor of those plugs). maybe that's what ruined the tci. i don't know.

i bought the bike recently with the running condition it was in. had to change the vacuum line and vacuum port caps to fix the leaks. also put new intake gaskets. as 2 were leaking and NONE of the brand new boots were tightened down.

all i can say is the tci was replaced and now the bike runs like it's supposed too. haven't taken her our for a drive yet. but hopefully my mileage has improved also. i was only getting 100 miles on a full tank.

the first bike when i had it 25 years ago. was brand new off the showroom flow. it got 200 miles. 60 miles per gallon. but the speed limit was 55 back then and i weighed 80 lbs less.

i was thinking about taking the thing apart for kicks and giggles. and seeing what happens if i replace the chip. i took electronics back in high school and have used a iron in repairing wiring on previous bikes past. so i'm pretty good with a soldering iron.

pm your addy. and i might mail it to you.

 

Ok...if you have a plug "cap" with 185k ohms then look to
ohms law for your answer.
too much resistance slows down electron flow= low or no
performance. High resistance blocks the flow of current ( amperage).
Low resistance and you have too much amperage.
My plug caps are supposed to read 10k +/- 15%.
I would s#!t if it was 185k.

 

What do you mean by (ground strap) im new at this.

 

as stated in the above post the tci was advanced in timing. probably running at a constant 35 degrees advanced. (or close to it).

vacuum line to fuel switch replaced. vacuum cap replaced. carbs gone through. fuel switch gone through. plugs and oil changed. plug caps replaced. intake gaskets replaced. all basics that were found bad were fixed. fixed the oil leak at the tach cable and fuel leak at the swtich also.

TCI REPLACED. HOORAYYYYY. BIKE FIXED. all in that order over 4 weekends.

 

Streetmmaster,
The ground strap is just one of the names used for the piece of
metal that sits over the center electrode-the place you set the
plug gap.
Hope that helps.

 

Oh i see said the blind man. :idea: