Triumphrat

kiwee · 03-16-2008

Tiger back on the road now after a COMPLETE (head to toe) engine rebuild. I have a few frustrating issues that I need help to diagnose.
First of all, everything on the engine was done during or just prior to the rebuild including new carb and new valves, guides etc.
Th carb has got all standard jetting as per the book with the needle in its central position.

1. After setting electronic ignition with strobe light I went for a ride and she "pinks" like mad under acceleration.
2. Reset back to setting I had before using stobe light and "pinking" gone but according to stobe light the timing mark is approx. 3/8 inch (9-10mm) to the left of where it should be!
Also when at this setting she idles ok but has bad flat-spot if you give the throttle a blip.
3. Dont know if this will help with diagnosis but following riders commented today that on decelleration ONLY there is a very small amount of light blue smoke. Engine runs absolutley clear all other times.

So Im not sure if I have an ignition or carb problem or both.

Any ideas gratefully recieved.

TBS · 03-16-2008

what octane fuel are you using?

TRI-AL · 03-16-2008

You probably won't believe this, but I had the exact same problem until I switched BACK to the original points/condensor set-up! The pinging improved immensely and it generally runs a lot better! Why? Beats the heck out of me!

abmar · 03-16-2008

It might help if you posted some details of your machine eg year, engine size and any modifications from standard including the type of ignition system fitted.

Having said that my '70 Bonneville with a Boyer ignition system works fine. Are you sure you are reading the correct timing marks? Have you followed the fitting instructions exactly? My instructions say to time the motor at rpms in excess of 5000 to get full advance.

In any case they will all pink on modern fuels when the throttle is opened abruptly from low revs.

panda · 03-16-2008

Firstly the timing marks are a general purpose starting point. run ignition as far advanced as you can -without- it pinging. Be aware by installing electronic ignition you lose the abilty to start it with a flat battery.
Other things to check..
right grade of plugs fitted with right gap ( too small gap advances ignition)
make sure you are not running weak
do not worry about the blue smoke, it is just oil being sucked into teh combustion chamber on the overrun.. My 500 did it when new and after its first rebore....but oil level was fine...doesn't take much oil to make smoke.
and as has been mentioned, fuel grade.
Sometimes a sharp edge can cause a hot spot inside the combustion chamber to give pre-ignition. changing the timing wont affect that at all, and anyway it is a very rare condition.

kiwee · 03-16-2008

Sorry guys, more info for you. I thought my bike details were on my avatar.

I have an 1981 Tiger 750
No modifications from standard factory setup other than being bored to .040"
Have run 91 and 95 octane fuel..slight (very slight) improvement with 95 octane.
NGK B8ES plugs
Standard Factory Electronic Ignition.

Friend told me today that the timing marks were general starting point. There I was thinking the manual was to be taken as fact? Doh!

peintremondain · 03-17-2008

hi,
pinking is caused either by over advanced timing or too lean carburation.
if your timing is spot on then it's too lean.
i had this problem with a tr6 and i finally found that the slide cut was too lean :i changed from 3.0 TO 2.5 and pinking was gone
check also your float bowl lever too;too low makes mixture too lean
try also to put the needle one notch up
benoit