help in building my yz 490 up

[blaster 22]

I have heard the trick behind alleviating detonation was to change the carb to a 38mm.I guess reworking the head isnt the best way to go about it according to Eric Gorr.I have a 38mm form a newer bike that im gonna try and run,i'll see how it goes.It'll run hotter with 2 base gaskets plus your port timing will change so thats not the answer either...from what i have "heard",some may have had success though.Mine is going in a 250r quad frame right now.Im a few days from firing her up.It may rattle a bit but hopefully i have that vibration problem solved

[oldschoolzuk]

My buddy had one early 80,s maybe 85 and my 89 cr500 could not even touch it.That bike had so much low end grunt it would just rocket out of the hole and just swamp berms.It was definetly a different kind of beast.He had some aftermarket parts on it but mostly stock.The air cooled head was huge.The bike ran great when it started,He also had a technique for starting it simalr to what is stated here by tipping it and kicking the hell out of it it would fire up easily.I rode it a few times and loved the power but it rides like a log.big bulky and lanky but the suspension was ok.Overall a fantastic bike with huge potential.I am glad to see that someone else is bringing back a major piece of racing history.Awesome !!!!!!!Please post pics of your progress and be sure to send a vid of it running........Good luck....