Hey Gang,I have a 83 Brat with a Hitachi carb and 150,000 miles. So all has been well till a month ago it started to have a high idle once it warmed up,like 2,200 RPM's.  I cleaned and oiled all the linkage and that helped some.It now goes between 600 RPM's and 2,200  RPM's.   More than once after going 10 miles it will drop to 6 or 700 at a stop.Today I drove it 3 miles to the store..High idle ,drove back home still high.I opened the hood and tryed to manualy turn the throttle back but no go.something is holding it high..the cable has play in it so that should be ok,must be linkage related..any thoughts?  thanks ,Todd 

My 85 had the same issues. Sounds like its about time for a weber carb swap.

weber carb is definitely the way to go, however if you are dead set on keeping your hitachi... it really sounds like you are having vaccuum problems. just go along every hose with your eyes and look for cracks or dry rot.

Sounds like a classic vacuum leak.

Cool.... I'll look into that and let u know,Thanks Todd   I

my vac leaks were internal with the carb, I purchased a rebuild kit from o'rileys for like 25 bucks. replaced the gaskets, accelerator pump, check ball etc.. 

 

i was still having vac leaks so I used a cigar (while car is not running) and blew smoke into the intake and you could see where the leaks are. i had to chief down and entire cigar but don't give up! they will appear… i promise. 

 

the other classic vac leak is where is EGR connects. 

 

After dealing with this for a few weeks, I decided to go with the weber. If you have any questions about the weber just let me know. I can show you the exact parts to get to complete the installation.

I may go that route but for now....I have a vacuume guage on my dash and it reads the same, 22  weather it was idleing at 700 RPM's or 2,200 RPM's and i can't turn the idle down by turning the throttle back.Its solid,so I'm thinking the linkage is jammed somewhere. I need to take off the air cleaner and see what could be holding it back...hey thanks for the info...I'll be back.... 

Sounds like the fast idle cam is hanging up.

Confirm  that the fast idle screw does not touch the cam behind the choke thermostat after the choke opens.

Not unusual for the cams to gum up and stick.

 

I would also check that the secondary throttle is not hanging open.

I had to put a spring behind carb to pull secondary closed. I'll take pic if you need.

That would be great. I have never been to hot on these "New Fangled Carberators"..Other than RxR..I know webers and old school one barrels.... so yea any pictures would be cool,thanks,Todd

Well to all you folks loosing sleep thinking about my wierd carberator problems..... You can sleep tonight..after checking this and that  it turned out that the butterfly valve is loose in the carb, I was checking for leaks with carb cleaner and I sprayed some on the side of it and Bingo..started to stumble. I tried to rock it up n down and sure enough it had freeplay... so unless i can find a new hatachi for $250 bucks I guess i'll be doing a weber soon. Thanks again for all the imput,Todd

glad you figured it out! weber all the way! so much easier and simpler that way

Hey Naru... You were right .I thought the slop in the butterfly valve was causing the fast idle. No...It was the linkage behind the choke housing.....Cleaned it good and light oil and Bingo....all is well.   and once again..Thanks to all,todd

I had to put a spring behind carb to pull secondary closed. I'll take pic if you need.

I would like to see that pic, having similar issues, weber is standing by waiting for me to give up...