Rear Cylinders dead.

[mechanic1]

Help!! First off,....excuse my ignorance....But I need help and fast! I have a '86 venture royal.....great bike....but recently....after a long down-time (almost a year) of not running I bought a new battery and got it fired up. Naturally, I wasn't to suprised when It wasn't running perfectly....figured old gas....so....sea-foamed,....and later tried techtron that I have had very good results with also. Ran it for a quick and although shot road test.....loaded it up with myself ,.wife and camping stuff and headed out. got about 35 or forty miles and it prgressively got worse so turned around and headed home. By the time we got back....hitting on only the front two cylinders....and burnt about half a tank in that short distance...naturally.

So,....checking it out....sure enough....back two not firing....so quick went and bought some new plugs and put them in.....ran like a sewing machine....for about 1.5 miles.....same mis-firing came back.

Now,....have read a little on here about something called a TCI.....but what is it and where is it. suspect it is a major ignition componet??? Also read about some memebers experiances with connector problems....a 6 pin? Again...where is it. I don't own a service manual for it sadly.....never had any real problems with it since I have owned it. Help! appreciate a point in the right direction

[dingy]

The TCI is the 'Brain' for the ignition system. It is the source of the timing settings for the bike.

 

There is a six pin connector on left side of bike, near the shock damper valve which is just forward of the passenger peg. There are 5 used spaces in this plug. I saw one were it was full of grit and bike started after cleaning it and ran somewhat decent.

 

Another suggestion is to run a heavy dose of Seafoam through it a couple of times. Walmart and auto parts stores carry it. White can with red lettering. Half a tank, half a can, then run the heck out of it. Doesn't fix everything and has been known to foul plugs.

 

Gary

[KIC]

I'll let other talk about the TCI. You might check your plugs as Sea Foam can foul them out. Also, check the fuel filter and when you pull the plugs check your Ohms from the plug cap to to the accessory power screw in the fuse box. Should be 24 Ohms if I remember.

[mechanic1]

..I forgot to mention.....I removed the fuel line on the discharge side of the pump and ran some fuel out into a clean glass jar.....no trash or water.....also filled with fresh premium gas.....still same, same....so don't belive I have a fuel problem. The bike also made a wierd noise once or twice while cranking...almost like a "kick-back" firing...didn't sound to good. Is it possible I have a ignition pick-up going bad?

[mechanic1]

When I put the new plugs in the rear cylinders....the bike ran like a scalded ape....but only for the one mile or so then same, same...What is the compression on these things suppose to be?

[mechanic1]

Ok,...here is an update.....Took the new plugs back out of the rear cylinders.....cleaned them up with some gas.....noticed I had maybe to much oil in the bike...so I drained some out.....checked to make sure no gas in the oil....guess I just put to much in it back when I changed it. So now the level is well between the lines in the glass. Put the plugs back in and fired it up.....was running on 3 solid and 1 seemed weak.....sitting on the bike...the right rear is the weak one....fresh gas, full tank so I put the rest of the seafoam I had in(about 1/2 a can......took for a check ride....ran pretty fair but as I opened it up a little noticed it starts mis-firing between 3500 to 4000 rpm....seemed to get worse as the bike heated up more and more with more running time...

 

So I'm racking my brain....thinking....valves to tight maybe.....ignition componet failing with heat....or starving for fuel at higher rpms....but don't really seem like a fuel problem...thinking it would be all cylinders unless crud in one carb....increased resistant with heat somewhere maybe ignition related....tell me whet ideas you have guys...Also....was going the check the compression on those two...but my auto guage is different thread size so is there an adapter I can get?

[bkuhr]

The spark plug CAP has a resistor inside. With meter, OHM out inside of cap to frame ground. Forget exact spec but I think it should be about 2000 ohms (compare to one of the others) If way high, or just plain open, it would account for weak spark.

 

The cap can be unscrewed from the wire, and the resistor can be removed from inside the cap for cleaning of corrosion(watch small parts and spring), but likely I would just get a new cap from MC dealer for about $5.

[mechanic1]

Thanks for the plug cap tip....will check.

 

...Removed the airbox,....battery and box to get to the TCI....like to have never got the right connector out.....very, very green with corrosion. Gonna try and remove it and clean the connector and blades for a better connection and hopefully my gremlins or at least some will disappear...lol:sick:

[jasonm.]

I'll let other talk about the TCI. You might check your plugs as Sea Foam can foul them out. Also, check the fuel filter and when you pull the plugs check your Ohms from the plug cap to to the accessory power screw in the fuse box. Should be 24 Ohms if I remember.

Alway start with the simplest & easiest to check thing. Spark plug caps can go bad. BUT Yamahas can be disassembled, aka= cleanable. Check the resistance...should be about 10k ohms per the yamaha manual. I have found them 14kohm on bikes...aka bad. Which is fine if you were to use non-resistor plugs. Next check all connections as others have mentioned. TCI is under the battery. Taking out the batter box, you will see the 2 large connectors. But connections usually do not go bad in 1 year if the bike was stored in a garage. I see you say they are green...hopefully that's the root of your issue. Or you wash your bike a lot. Another reason not to wash your bike...water gets into connections. If that's not it. There is a high probability it's carbs just flooding the engine...bad float needles...just worn out, aka gas too high in carbs. It happened to me. along with "sinking floats". Damn ethanol.

[Trader]

When you put it all back together, get some stick on velcro and just mount the TCI on top of the air box. That way it is much more accessable in case of future problems.

 

The cable should be long enough...it just sort of flips up and over.

 

You may have to cut one of the mounting tabs so it will slide far enough forward to clear the top of the tank cover.

 

 

Most folks do that.

Probably a thread on here about that somewhere.

[KIC]

Alway start with the simplest & easiest to check thing. Spark plug caps can go bad. BUT Yamahas can be disassembled, aka= cleanable. Check the resistance...should be about 10k ohms per the yamaha manual. I have found them 14kohm on bikes...aka bad. Which is fine if you were to use non-resistor plugs. Next check all connections as others have mentioned. TCI is under the battery. Taking out the batter box, you will see the 2 large connectors. But connections usually do not go bad in 1 year if the bike was stored in a garage. I see you say they are green...hopefully that's the root of your issue. Or you wash your bike a lot. Another reason not to wash your bike...water gets into connections. If that's not it. There is a high probability it's carbs just flooding the engine...bad float needles...just worn out, aka gas too high in carbs. It happened to me. along with "sinking floats". Damn ethanol.

 

 

Maybe somebody else can clarify, but my understanding is that if you check the plug wires from the cap to the accessory hot lead in the fuse box it should be 23 - 24 Ohms.

 

The caps themselves should be 10 Ohms.

[bkuhr]

Maybe somebody else can clarify, but my understanding is that if you check the plug wires from the cap to the accessory hot lead in the fuse box it should be 23 - 24 Ohms.

 

The caps themselves should be 10 Ohms.

 

With cap removed should be 10K +- 10%

 

Testing thru the coil would add secondary coil resistance of 13.2k +-20%, and the hot lead of the coil actually makes is way back to the IGNITION fuse, not ACCY fuse.

[kentuckyrider]

When I bought mine number 3 was dead. Later another cylinder was running rough. I tore it down last winter to fix some oil leaks and replace the carb holders. When I took my coils out all 4 were cracked on the bottom. 2 of them tested good, 1 hit and miss. I replaced all of them along with new caps, wires and plugs and it has a lot of power now. Amazing how much when all the plugs are firing...

[mechanic1]

Ok...all good info to know......can anyone tell me what the compression should be on a '86 1300 ?

[dingy]

PDF cut of service manual for compression check.

 

Reader's Digest version is 142 PSI min, 192 PSI max. 171 PSI avg

 

There should be no more than 10% variation between high & low cylinders.

 

Gary

[mechanic1]

Thanks.....that is what I was estimating...going from the owner's manual that says 10:5 to 1.....

[mechanic1]

Ok.....after much running around...I finally got myself an adapter made for my compression guage.....readings go like this.....#1....140psi....#2......123psi.....#4.....same or very close to #2(123psi).....#3.....130psi....gave #4 a shot of oil and re-tested....very little change.....so don't smoke or use oil and it seems to get worse misfiring the warmer it gets so...I"m thinking the valves are to tight. ...tell me what you think guys.

 

Oh....also, the bike has right at 41,000 miles on it so really don't see it having worn rings and such.....however have serious doubts if the valves have ever been checked or set on it....no I haven't.

 

So what are the chances the valve cover gasket is re-useblem after 15000 miles of heat and cool? And Where does a guy get the valve adjustment shims and the tool to compress the springs so you can change them? Anyone got a that stuff close to me by chance???lol:fingers-crossed-emo

 

....?...unrelated issue....when I was into it removing the TCI....on the left side....near the front...there is a Green two wire connector....wasn't attached to nothing...anyone have an idea what that is for(didn't notice the color of the wires.

[bkuhr]

My feeling is your compression is not a major problem, but if you feel the need a more useful test would be with a leakdown tester

http://www.harborfreight.com/cylinder-leak-down-tester-94190.html

and you can even hear where leaking air is coming from,

ie:exhaust=exhaust valve, carbs=intake valve, crank case breather=rings

 

Recommend you do not even try to reuse valve cover gasket.

[mechanic1]

My feeling is your compression is not a major problem, but if you feel the need a more useful test would be with a leakdown tester

http://www.harborfreight.com/cylinder-leak-down-tester-94190.html

and you can even hear where leaking air is coming from,

ie:exhaust=exhaust valve, carbs=intake valve, crank case breather=rings

 

Recommend you do not even try to reuse valve cover gasket.

 

OK...wasn't sure what kind of material the gaskets were made of.....approx. cost?

 

I am familiar with leak-down compression testing.....requirement on small aircraft engines old A & P mechanic)

 

Was kind of thinking since the bike didn't have that many miles....and compression was quite a bit lower than the min on all cylinders and fairly varied....and it seems to get worse as things heat up ..(and expand and grow like valve stems...) ..but it is a better test. Thanks

[mechanic1]

Please tell me your idea's of what it might be Brian. I'm always open to suggestions...and naturally lazy too...lot easier to listen to what folks have to say rather than be a hard head and do a lot for nothing...lol

....got coils and such in my head also...

[skydoc_17]

Hey Roy,

Here is a low cost test to make sure the coils are good. Swap the spark plug lead and the terminal wires from the two "Good" front coils to the rear two "Bad" coils. With the bike cold, start the bike, and see which exhaust pipes get hot first. If the two front good cylinders are now cold, and the two rear bad cylinders are now the hot ones, then you know the coils are bad on the two rear cylinders. If nothing changes, then you most likely have a bad (intermittent) TCI Unit. The Carbs. USUALLY either function, or not. They don't usually run good at start up then degrade when the engine gets hot, USUALLY. BUT a TCI will be adversely affected by the engine heat. (As will the coils)

When you do the "poor man's" coil test, you need to swap the spark plug wire AND the leads for the primary windings in the coils as well. If you find the TCI is in fact Bad, there are three options, New from Yamaha, (ouch) used from Ebay, (You could spend $100 + for another bad TCI unit) and lastly an aftermarket TCI from Dingy. (Gary, who posted earlier in this thread)

If you go the Ebay Route, then you need a TCI from a 1984 to 1989 VR. The 83'VR TCI won't work, and the 1990 to 1993 won't work either.

Try the coil test and let us know what you find out.

Earl

[bkuhr]

Please tell me your idea's of what it might be Brian. I'm always open to suggestions...and naturally lazy too...lot easier to listen to what folks have to say rather than be a hard head and do a lot for nothing...lol

....got coils and such in my head also...

 

These engines are rock solid, and I would not read to much into compression #s. My #s were about the same, but when I finally got it to start pulling on all cylinders, the low ones started coming up.

 

In my opinion, both the ignition and the carbs are very finickey.

 

ignition-check spark cap and wires, I found corrosion and bad resistor here

 

ignition-flakeyTCI, I found bad diodes here-find someone to try swap with. The ingtitech option is the best but cost ~$250, Do relocate the TCI to top of airbox, you will be glad you did.

 

ignition-cracked coils-try coil swap Earl suggested, must swap the 2 wire connector on coils as well as the HV lead.(keep track of where these started at, suggest paint marker both halves of 2wire connector cylinder#)

 

carb-I have cleaned my carbs 3 times, finally running pretty good but still can't adjust idle mix on 2. My mgp is 30(suspect I have sync and main fuel higher than normal to compensate for no(plugged)idle mix on, sucking main fuel at idle and killing my mpg.

I plan to buy ultrasonic tank and try again-just not during riding season.

 

carb-sync is a must, buy a 4cyl sync tool. You will be glad you did. Every time you get something fixed(ign, carb) and it finally starts pulling, your sync will be off from where it was when a cylinder was not pulling

 

carb-vacum leaks. Leaks screw up everything how a carb works. I spray ether(start fluid) under carbs and listen for RPM increase, try to hit all fittings&hoses. If so pinpoint where leak is at.

[mechanic1]

Ok....I'll check the ignition coil as suggested.....makes sense....easier and cheaper too...lol Thanks guys.....let you know what I find out...

[dingy]

....?...unrelated issue....when I was into it removing the TCI....on the left side....near the front...there is a Green two wire connector....wasn't attached to nothing...anyone have an idea what that is for(didn't notice the color of the wires.

 

The green connector you found is for a bike sold in California, it is on all the bikes, but only hooked up in Cali. bikes.

 

Per the specs in the manual, your compression readings are on the low side. Valve will be a good first thing to check. Are these readings with the throttle wide open?

 

Also, I have some spare coils if you find you need any. I don't use conventional coils on this bike, went to coil over plugs.

 

Gary

[mechanic1]

Thanks on the green connector....vale clearance check I think I will do....just don't have a gasket as of yet...so pushing that back a little and checking the ignition system first....The coils you spoke of....what is the cost? ...never had to do anything to this bike so far so all is new to me....lol ....valvee cover gasket cost? How about the valve adjust tool?