Hey everyone it has been a little while since I have been on the forums doing some wondering and reading and such, and I was recently tasked with adjusting the carb on a hijet model truck. I was able to get the AC and normal idle screw adjusted, but the mixture does not seem to smell too correct and if you take it out and drive it for awhile it will start to have very little acceleration in the gears... I will post a pic with the three adjustment screws that this carb has also. I can only assume the big one is the mixture since it does not affect idle whatsoever. I do have a G&R Imports shop manual, but it does not help much with tuning the carb itself.
pic is missing also check here the repair manuals MrJPolito uploaded https://minitrucktalk.com/threads/japanese-service-manual-download-s100-s110-s120-s130.21820/
The GR site has a good set of pictures of the carbs with the parts, and adjustments identified. How are you setting the idle mixture? I did a post of how to set best lean idle. Search for it. Adding: the thread is some thoughts on carburetors Search for posts by me, with carburetor in the title.
I'm going to go out on a limb but I think I stumbled upon the truth. I haven't seen it described this way so forgive me if I've missed this information elsewhere and/or it is incorrect. 1= Cold Idle (startup) adjustment 2= Idle adjustment 3= Throttle-up adjustment (a/c)
I've the same carb and that labeling is how I think it is too. Though I sent an email to g&r and they told me 2 is a/c load idle and 3 is hot idle. I think that there was some miscommunication because from what I can tell from making adjustments, your diagram is correct. I tied adjusting it to idle with #3 and it would over rev when it got hot then die if I adjusted it back to a low idle. My guess is the load from the fan would bring it up, and if I adjusted back to low idle it would die when the load was no longer demanded. Don't have that problem now that I'm back to tuning according to your picture
The white nylon thing is the idle mixture screw. Depending on your elevation, you may need to pop it off to actually adjust the idle mixture. I'm at 4500-ft, so the idle was way too rich with the cap on.
Thanks Kevin, I know the one under the cap is the air mixture, not sure if it should be 1/1/2 or 3 1/2 turns out from seated. I've found both numbers on threads here, one must be a different carb. Mine was set to around 2 1/2 before I took the cap off, I think around 3 turns out seems right for it according to the plugs. What I'm unsure about is between screw #2 and #3, which is the a/c load idle speed and which is the hot idle speed adjustment. I'm 99% sure that the the way it's labeled in the picture is correct. Can anyone confirm this?
Jigs confirms the labeling of the screws in this thread: https://minitrucktalk.com/threads/throttle-pull-down-rpm-drops-too-slow.20161/ It is correct
Just realized it was you I was replying to and not Kevin, confused two threads. Thanks for all your postings! Don't know how I'd have made it this far without the help from all you folks on this forum!
