Well, with all the cool modifications I have been reading about of late. I decided I would take the leap of faith and throw my hat into the ring. So I previously modded the 34 mm stock carb by oval boring it to a little under 35mm. Today I took the carb off the bike and filed and dremmeled it to 35.98 mm. Almost 36. It took about an hour and a half. Index finger is a little sore holding that file. The bike has been burbleing a little bit at about 2 or 3 thou rpm so I am hoping if it is rich there the bigger carb may solve that, dunno will try it. I have a 200 main so will see how it performs. I decided to start another thread on the bikes progress. After the carb, it's not installed yet, I want to close the squish to about 30 thou inch and perhaps try 150 psi compression.

its important to know at what throttle position tuning issues are happening in order to make sugestions . So if the new carb has issues that where you begin.

Rich

Your so right I will start with the new carb and see whats going to happen. Yah i hope to get it back on today. At the apex of the cressant I have a wall thickness of 1.05 mm which is why I stopped at 36mm. All is good just have to do a minor modding of the intake manifold to match. I want to give a check the reed valve while in there. Another issue I have been having is the bike does not want to start cold if I go past 2 or 3 kicks it floods out and won't start the rest of the day even turning the choke off.

Interesting, I found the jet needle in the last bottom groove clip position so this raised the needle. Does this position inrichen the fuel supply? I wonder which position to set it for a ported motor to start with. I know stock is the middle. That may have contributed to that blubbering at mid rpm. I found the position by accident as I have been working on getting the throttle slide to go up and clear the carb bore at full throttle due to raising the roof of the bore. It may be a combination of grinding the top of the throttle slide down a little and then a cable adjustment. I have gotten it to a half mm or so just.a little bit more hopefully tomorrow. I did accidentally drop the slide on the concrete. That sukd a little and bent the needle. I'll try and straighten it tomorrow.

needle position wont affect starting if your doing it right ( throttle closed ) if your pilot jet is too small you will have issues starting

Rich

Yes it might be the pilot thank you rich. I cleaned the carb so hoping it might have been dirty. If not I will go to yamaha and get a larger one. On a side note I checked the reeds, still looking good. I am going to ditch the gasket to use some yamabond and see about any improvement performance. Also, I didn't mention I had a oil/fuel leak between the hardened up intake manifold and reed valve but since tightening it up very good haven't been leaking oil out the bottom of the valve. So a little yamabond on that too. Got the needle straightened and slide clears the bore. Turns out the slide needed grinding at the top and cable adjusted. Edit, the por-15 porpatch is still rock solid in the cast intake manifold after 200 miles so that's good.

Got it together just waiting on the yamabond to harden a little then go through check the idle hopefully it will start, then give the oil pump pulley an adjustment if needed due to an adjustment I made in the throttle cable adjuster at the handle bar

So I think I may play around with the jets on the oval bored carb. It is now running will see with some jetting changes if it performs better than the stock 34.

I would say definitely keep your 34mm carb if you have a stock dt. Unless you can get one with same velocity or greater. I am keeping the 36 for now because I may raise my cylinder, but with the 36 I may have just a touch less on the bottom end but just a touch more on the top end. Not enough at all of a difference to warrant the loss of some low end. Keep the 34.

FrankC wrote: I would say definitely keep your 34mm carb if you have a stock dt. Unless you can get one with same velocity or greater. I am keeping the 36 for now because I may raise my cylinder, but with the 36 I may have just a touch less on the bottom end but just a touch more on the top end. Not enough at all of a difference. Keep the 34.

Thank you for an honest appraisal of your modification attempt!