Hi, I am hoping you guys can help. I have spent the last few days trying to fire up my recently assembled 1990 1000F. She simply will not start and I am past annoyed. The carbs are surgically clean and pilots are out 2.5 turns as they were before I stripped them down. The fuel that was in the tank has been dumped and fresh fuel put in. I have checked the cam timing again, its 100% correct. I have put a spark plug on one of the leads and laid it out on the tappet cover and swung the motor. It does spark. I have opened the carb drain and can see fuel flowing out so fuel supply is fine. What the hell?? Not so much as a sputter or backfire. NOTHING. Just ages of cranking and swearing and rechecking more cranking and more swearing. This motor started out as a running SC21 motor. I fitted it to this bike and swopped out the pulse generator for the single version so the wiring worked out. I then changed the head to a SC24 one so the water pipes fitted. I see no reason on God's green earth why the %@!$!@% thing still won't start. Any ideas appreciated. Sorry for the rant but I am sure we've all been there so I guess you will understand

Thanks in advance

 

Ok, let's be logical and methodical about this David - and I understand your frustrations fully.

Motors generally are quite an easy process to turn petrol into bangs and forward movement.

We need fuel, compression, a spark, a detonation and rotation of the crankshaft. This generally brings a smile to the face if in the correct order.

And not if the sequence is not in the right order.

OK, so you have spark. Is it a big, fat blue spark when the plug is earthed and the motor cranked? If not we need to look at the coils etc.

Is the motor cranking at the right speed? Ie. starter may be cranking correctly but alternator damper slipping and not allowing the engine to turn at full speed.

Otherwise, it sounds like your fuel vapour and spark are not meeting up. Are you absolutely certain you don't have the timing 180 degrees out? Plugs leads are in the right order?

When I get to an impasse like that, I sit down with a pad and paper and check each item methodically, eliminating all possibilities.

Good luck and let us know how you go.

Cheers, SB

 

are you running a fuel pump, i had a bit of trouble with mine, can you smell fuel like shes flooding, if not try gravity feeding to start just to check the foat bowls are filling right up , check your fuses as one of them covers the fuel pump, then as s.b says work your way through everything i know its a pain when you have done all the work and she wont play ball

 

Which CDI unit did you use ?

 

I might be missing something here, but ignition timing being 180 degrees out won't stop the bike from running. Its a wasted spark system so firing order of 1-2-4-3 180 degrees out gives 4-3-1-2. Since 1 and 4 are the same coil and 2 and 3 are the same coil it would make no difference at all IMHO.

There is no fuel pump on this bike. Gravity feed with a vacuum tap running off the side of no1 carb. It is running the SC24 CDI as well as the single coil pulse generator off the SC24. I also swopped the 7 pin generator wheel to the 9 pin the SC24 is meant to have so its all the right parts in there. Will be fighting with her again tonight, will report back if anything works. Going to try my other set of carbs and another set of coils to see if it makes any difference.

 

I'm starting to doubt my mechanic friend. He says the cam timing is right, but if I put my hand behind the carbs I can feel them blowing backward. This is what I found when I had a look. Is this right?

Timing mark



Intake cam



Exhaust cam



Sprockets

 

I found the problem...

The guy who came over to help me swop the heads had a blonde moment. The cam timing is 100% correct...pity the exhaust cam is on the intake side

He musta been having a blonde moment... Can't wait to rag him on this one

 

Well done finding the problem.

Do the cam swap and let us know how you went.

Cheers, SB

 

That's the reason they have two cams.

Just to mess with your head.

You're not the first to have ever had that happen, and you definitely won't be the last.

An acquaintance of mine (who is a mechanic) managed to screw a Subaru boxer engine together with the cams swapped on one side only.

Dam near drove him to distraction.

 

YEP! The cam turns at 1/2 the rpm of the crank.


Not on planet Earth. LOL


NOPE!

Your cams are installed correctly but timing is off.

With the timing marks you have in the photo. The "IN" should be in line with the rear surface of the head while the "EX" is in line with the front of the head surface. (Cams are in proper holders). In the photo of the sprockets you have the word "UP" at the bottom of the sprocket and it does make a difference that it should be at the top for proper cam timing.

Don't move the cams but time them the proper way and she should run for you.

The way you have them, she is sparking at the bottom of every stroke on all cylinders.