Bonneville America Forums Forums Technical Forums General Tech engine No,s

I bought an engine from a wreck and not completely sure what it is. Someone has written 2003 Bonneville on it and the Eng No. is Y181095. I,m not sure of its capacity or degree of crankshaft firing order as I believe there is two different capacities and Degrees.

If its a 2003 motor it will be a 790cc the firing order can be determined by removing the spark plugs and using a dial gauge (or even a screwdriver) to check if both pistons are at tdc at the same time - then its a 360 degree (std bonnie) if not its a 270 degree (SM/BA)

Hope this helps

Jan

Thanks for the info, if its a 790 would this then be considered the inferior of the two different design engines? and are the power characteristics dramatically different ? and would this engine be suseptible to some tuning mods ie: carbs , big bore kit, head work etc?, I dont suppose cams or cam grind information is available.
I dont ask for much do I?

Don,
I wouldn't say that any of the engines are either superiour or inferior. They merely have varying characteristics. If you have an '03 engine, you have a 790. Depending on what it came out of, its either a 360 or 270 firing order. Your HP and Ft.Lb. ratings are posted the same. The biggest difference in these two 790's - sound due to the firing timing. Later years have more variations.

If you want to get rid of your "inferior" motor cheap I'll take it off your hands

Jerry

I dont wish to sell .I,m building a Triton. I have fitted the engine to a Norton Slimline frame specifically constructed to accomodate this engine. After the bike is finished and sorted I am considering some tuning mods and was thinking along the lines of maybe some head work carbs, cams if I can get enough info.

You could always stick the Wiseco BB kit on it, have a read through the archives and find out what gives Don.

I,ll certainly be considering the Wiseco Kit. I think I,ve just determined that my engine is a 270 degree version, when one piston is at TDC the other is down 37.5mm.

The 270 is actually a superior design - as it has 90 deg separation between the cylinders it has better primary balance and superior power delivery characteristics. See the following link for more details.

parallel twin timing discussion

BTW your idea for a new Triton sounds like the business - keep us posted on how you're getting on. Photos would be good

Regards

And there has been a fulsome and useful discussion on cam timing: Cam timing

In short, the 790 cc cams are far better than those from the larger displacement (factory) engines..
Jan

I tried to post photo today but it said it was to big to load. I,m not real good at this stuff.