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Can't get cbr900 to start
tompat3463 - 13/5/14 at 09:15 AM

Just finished fabricating the exhaust for my mini got the cbr893 engine all wiring up but will it bugger start

I've had the engine running superbly on an engine stand and the only thing I have changed is the spark leads to accuspark leads so I could relocate the coils. That's my biggest question mark at the minute

I've taken the leads out the sockets and there seems to be blackness on the point where it should be contacting in the coil. Is this normal or does this mean it is arcing ?

The engine is turning over well and occasionally flutters with full choke

It used to fire up no problem on the stand.

Also can I just check that all 3 black and white ignition wires should be to a positive ?

And also I buggered the neutral switch connector so until I fix that I have earthed that green wire.

Any help welcome

Alan

jossey - 13/5/14 at 09:41 AM

How are you fueling it?

From a tank etc?
Fuel pump?

tompat3463 - 13/5/14 at 09:43 AM

Ali tank on boot with cbr pump. Definitely getting fuel as the plugs are damp

mark chandler - 13/5/14 at 11:22 AM

They are incredibly sensitive to plugs!

Take them all out, heat with a blow torch then install as quickly as possible so they stay hot and try again.

woodstock - 13/5/14 at 11:27 AM

I have a 919 and changed the leads on mine. I found that even small changes in the length affected how well (badly) it ran.

Since you say you changed them for relocation i'm guessing you've made them longer and may be having a similar but exaggerated issue.

I'd test by swapping the old leads back on, extending from your loom to coil pack if needed. If it then runs fine you know it's something to do with the new leads. If you have enough spare lead I'd cut one the same length as an OEM lead and confirm that runs ok (cable is good enough). You could then mess around trying to extend them.

Personally, I'm going to make up a new bracket to hold the coil packs in a closer location so i can run OEM length leads.

Hope this helps

Chris

ReMan - 13/5/14 at 11:37 AM

All aboev, accuspark leads broke my mates car recvently

But you Pull a plug out and see if its sparking at all first

andyfiggy2002 - 13/5/14 at 12:04 PM

interesting, sorry to go off topic but is it really crucial to have all 4 sparkplug leads the same length? if so i will need to invest in some new leads as i made custom ones of varying length instead of using the bike originals not thinking it made a difference

ReMan - 13/5/14 at 12:37 PM

No they can be any length within reason

tompat3463 - 13/5/14 at 01:14 PM

I don't seem to have an excellent spark to be honest

tompat3463 - 13/5/14 at 01:25 PM

Also. I've just pulled a plug cap off and tested continuity from the coil end of the plug cap the where it fits over the plug and there is no continuity. Surely that can't be right. Surely the cap is just a bend bit of wire effectively connecting the ht lead to the spark plug. I've checked them all and they are all the same

Eh !!!

ReMan - 13/5/14 at 01:30 PM

quote:
Originally posted by tompat3463
I don't seem to have an excellent spark to be honest


There not always as strong as you'd expect they should be, but still normal.
I expect, that this is what makes them so sensitive to wet plugs.
Nevertehless, I'd expect if theye all sparking (notwithstanding my commebnt about Sparkrite leds) that if you dry/heat them over a gas ring/blowtorch that it will work. Be carefuil with your choke though, almost unneccessry

tompat3463 - 13/5/14 at 02:57 PM

Finally got it started. But running lumpy as hell.

Removed a plug cap on 2 or 3 and it seem to fire into life and run smoother with the plug caps off !!!

This is doing my head in !

jossey - 13/5/14 at 05:39 PM

I assume you have the leads on right. Ie 1 n 4 then 2 n 3

tompat3463 - 13/5/14 at 05:54 PM

I'm 90% sure I've got the leads right.

1-4 from one coil and 2-3 from the other. I have a picture of my old Indy blade for reference and I'm sure I've got it the same as that.

I have just taken the carbs off to clean and looked down the ports while it was off. It all looks good apart from one valve seat which is rusted slightly.

I'm wondering if that valve isn't seating properly. But I've had this engine running great on the stand and is imaging that corrosion would have raked years to develope so I'm still no further on. I think a new set of plugs is the way forward now.

What should the spark gap be on these engines ?

ReMan - 13/5/14 at 07:01 PM

quote:
Originally posted by tompat3463
Also. I've just pulled a plug cap off and tested continuity from the coil end of the plug cap the where it fits over the plug and there is no continuity. Surely that can't be right. Surely the cap is just a bend bit of wire effectively connecting the ht lead to the spark plug. I've checked them all and they are all the same

Eh !!!


Suspect you won't get 'Continuity'
There'll be a resistance 5-10 kOhms at a guess

tompat3463 - 13/5/14 at 07:17 PM

Yeah had a read into that and that's what I thought

Has any body got a way to check which lead shoukd go where ie. left hand side of coil 1 to cyl 1 ect ect. Or could someone take a clear picture of theirs ?

Many thanks in advance