Crank shaft question
 

Hi guys.

Is there someone out there who knows if there is a diffrence between a 86 1vj crank chaft and the crank shaft from a 94 3TB engine? Since the 3TB has TCI ignition it has a smaller diameter on the flywheel than the CDI system on the 1vj. Is the stroke and timing degree the same on these two engines?

cheers.

Tom.

Shaft and conrod
 

I seem to remeber that the main engine dimensions (bore, stroke) are identical. Most probably the crankshafts themselves are identical. As for timing, doesn't matter, just how you set the camshaft.
The conrod is, I think, different.
To make sure, compare part numbers.

Auke

wierd starting problem
 

Thanks Auke

Yes that is right conrod is diffrent,but lenght is the same so that is okey.
I have spark ,fuel and the timeing is set as it shuld be but the bike still woun´t start up. When I crank it it fires up at once just to die off again. I have never experienced anything like it before. To me it seems like a timeing issue.But verything is set according to the manual.
In desperation I tryed to put an other carburator on yesterday,but it still behaves the same way,it´s just wierd.
Any ideas what might be wrong?


Tom.

If it starts then dies you either have fuel feed problems or something electrical is breaking down when it warms up. Unless you mean it misfires at higher revs then runs ok at low revs, in which case the timing is retarded.

No, it´s not like that. When I crank the engine, it ignites straight away,rotates one time and dies.i´t will keep on doing this for as long as I run the starter.
I have set the timeing too the marks, and cheked that the piston reaches TDC. everything seems to be okey.
I suspected that it was the magneto that was not in possition,since Im useing a CDI system on the engine now (originaly TCI) But everything lines up just like it did on my old 1vj engine.
Im seriously running out of ideas what to do:confused1:

It´s annoying,being so close too getting it running again,and then run in to this mystery problem.

Suspicion ...
 

That you have built a 1VJ engine into a 3TB frame. So, an engine with the stator and magneto for CDI ignition, the CDI installed on the 3TB 'platform'. Are you sure that the wiring loom is as it should be for CDI ignition?

Auke

More details to clar things up
 

Okey, I better explain what I have done in more details.

The bike I have rebuilt and modifyed is a 1986 xt600 Tenere. The old 1vj engine was damaged when I bought it,the previous owner had driven it with too little oil and had seriously damaged the camshaft bearings,and the conrod ws badly worn (lot´s of play) I did a feve temporary fixes on it and
it was driveable and it did the daily commuting thing well for a while.
One morning on my way too work it just died, turned out too be the alternator that had shorted out.
Then I found a 1994 3TB for sale on ebay,complete engine with carbs etc.. but no TCI unit.
Did some research and came too the conclution that I could fit my CDI system on the 3TB engine if I took the alternator cover and magneto from the old 1vj. Everything is the same except for the electrical starter.
Since the 3Tb has a smaller diameter magneto the oneway bearing is allso smaller. So I had to fabricate a new adapter to be able too use it (the bearing from the 1vj engine was worn out so I allways kicked that one.

Put in my new alternator and while I was at it I restored the loom on the bike as well,new connectors and relays.The guy that owned it before me had used the "cut away" method when stuff started to fail so Now I got the lights indicators and everything else working again.
Upgraded the head light too a dubble head light from KEDO,and put in an Oil temp gauge.
Since this model has a bad reputation for overheating because of the insuficent air flow around the top end, I relocated the oil cooler. It now sits infront of the engine on the left side infront of the clutch cover.
I built a headlight guard and a crash bar around the engine as well.
Wheels are original rims with heavy duty stainless spokes.Front forks got a set of progressive springs,the back is still stock.

There is a lot more but this has realy nothing to do with the thread,has it:cool4:

Any way, I got the engine in too the frame just before I went on vacation.So I only had time too start it once. It fierd up straight away,but dies as soon as I relese the starter. At this point I was sure it was just a clogged up carb since it had been standing for a long time.
Back after vacation I took the carbs apart,they look like new inside. Removed the filter under the floter needle while I was at it. Put everything back together and tryed again. Same result,It turns over nicely and fires but nothing more.
Took the valve cover off to dubble chek the timeing,nothing wrong as far as I can see there.
To rule out fuel problems I disconnected the fuel pump and tank, and gave it fuel straight in too the floater house with a chopped off bottle and a rubber hose. Same result again.
Adjusted valve clearance(again) just too make sure it was okey. Still the same.

It must be something Im over looking but what:confused1:
I have had many bikes,but I have never had sutch a problem after a rebuild.And the XT is quite simple in it´s construction.
It´s frustrating being so close to geting it on the road again,and then have this :censored: going on.

Well, Im sure I will find out what is wrong with it in the end. This forum is superb:thumbup1:
There is allways some one here too bounce ideas with or get some tips from.

Tom.

Hmmm
 

As far as I can tell, your bike now has a CDI ignition system with:
- 1VJ stator
- 3TB flywheel
- 1VJ CDI
- 3TB wiring loom

The CDI and the TCI systems are principally different. In the CDI system the energy to make the spark comes from one of the coils included in the stator. This coil charges the condensor (C in CDI) that discharges that energy through the ignition coil to produce the spark.
In the TCI system the condesnor is charged from the battery.

Summary, the wiring looms and working of the two systems are different. I think you will have to search in that direction, and choose either to combine all 1VJ components (including wiring loom!) with each other or all 3TB components.
I can imagine that the 3TB has a different flywheel, as it does not need to charge the ignition, only to produce electricity for the on-board net. Different magnetos?

Good luck,
Auke

1vj wireing loom
 

Hi Auke.

No Im useing the wire loom from the 1vj. I had a loom for the 3Tb system as well but since I didn´t have the TCI unit it self I decided to use the complete set up from the 1vj.That way I didn´t have to make any mods,and hoped I would have nice and easy installation:thumbup1:

I found a leak on the intake from the secund carb yesterday.A small crack between the aluminium foot and the rubber,fixed it but that didn´t help.

The mystery remains unsolved:cool4:

Now it gets interesting ...
 

So the bike only fires when the starter button is pushed, but immediately cuts out when the button is released?
Then I preliminarily conclude that sparks are only generated when the starter button is pushed ..... try the following: start with starter, till engine fires, then (acrobatically) unplug the wire from starter button to solenoid, all the while pushing on the starter button. Does the engine keep running?

Let us know ...

Auke

Another thought
 

Trivial, but, is the idle speed setting high enough to keep the engine running when the starter motor is switched off (you release the button)? Big screw on the LH side of carb, screw clockwis to increase idle speed.

Auke

On the off chance...

Check for voltage drop to the coil. I cant speak for XT's here, but I have experienced similar problems on other engine types. The plug resistance changes according to fuel/air mixture and compression (hence varying gaps). With the impetus / assistance of the starter the engine will fire, without it, the plug shorts across the cap. If this is your problem you will see pinprick carbon leaders in the plug cap where it's shorted across.

Good morning everyone.


Hmm....That is something I haven´t tought about Auke,I will have a go at it.But what could be the cause:confused1:
I have played around with the idelscrew alot,when I set it so that it just tuches the lever arm and then takes it up just a hint so that it starts to push I get the best respons from the engine.It will give me a detonation on every turn,if I go higher the engine starts to miss,and when it do fire I get a lot of smoke.I guess it get´s too rich and is about to drown.
The old engine was the same,it was sensitive to trottle until it had run for a couple of minutes and got warmed up.
Im running the stock jet´s and Mixture screw 2.5 turns out,needels are one notch below center. So I can´t see that any of this would cause the problem.

Plug resistance changeing with the fuel mixture / compression. I will measure the coil,but in my experience that problem only acures when you are dealing with high compression engines or superchargers. I had an old Chevy Nova some years ago with Highcomp heads that sometimes would do just that.

Anyway,again I have some new ideas and angels to attack the stuborn old beast from when I get off work today:thumbup1:

Thanks guys.

Sensitive
 

Normal that the XT6 engine is sensitive to throttle when stone cold. But that is opening the throttle by hand, not the fixed opening from the idle speed screw.
You say the needles are one notch below middle, recommend to set at standard setting: circlip on both needles in the middle notch, that's where they should be.
Counting from top, assume your needles are at 4/5, meaning carb is set richer than standard (Needles lifted one notch higher than standard). Could have some effect. Also, make sure all the washers etc under the needle clips are in place.

Auke

Had a long but not really awarding afternoon in the workshop, took out the trusty old multimeter and measured the coil. Got 0.28ohm on the primery and 3.8ohm on the secundary that shuld be okey.
Set the carb needels to center position and gave it a go, no luck.

Decided to find out once and for all that I don´t have any leaking valves. Got a little over 8bar on the gauge, according too the manual it shuld be around 8.5 so I cheked the valve clearance again but didn´t find anything wrong with it.
I guess it´s just the gauge,anyway that can´t be the problem.

To morrow Im going to buy a new sparkplug,the one I have is giving off a nice blue spark but who knows,plugs can do strange things and it doesn´t cost much to try.

I sugested too my wife that I put it out in the garden and plant flowers in the panniers,then at least it would be good for something.But for some reason she did´nt warm up to the idea. :cool4: