Topic: Breaking in with untuned carbs

[Madseacow]

I've just finished a rebuild with 850 weiscos, stg 2 cam and dual mikuni carbs. What should I do to tune the carbs while not risking the new pistons? I've started it for a few seconds, and it idles pretty high, it's loaded with gn4. The mechanic that's tuning the carbs says it'll be fine, but everytime I've broken in a fi car engine, I've used the high dollar stuff the machine shop sells.

Thanks in advance.


Sent from my iPhone using Tapatalk

[Tews19]

You may want to post in the HI PO section. I have no clue.

[ekpent]

As for tuning the carbs and breaking in the new engine I would make sure the carbs have a good bench synch,should be close enough to run pretty well. Adjust the idle with the knob and go put some miles on it and give it a proper break in by varying the speeds and loads. After a good break in then I would go back and change the oil then fine tune the carbs. Personally I would not want to be running a super fresh tight engine at idle for a long period right out of the box. Also you will not know how your jetting is doing etc till you get out and run it under a load, totally different than on the center stand.

[bjbuchanan]

Yeah the problem is that unless you get broken in runners with the same combo to chime in you ate hung out there. For the break in avoid idle and go out with average or recommended average jet sizes/ positions. You shouldn't be idling but you also shouldn't be racing for the first 100 or so. After that start to maybe tune a bit depending on throttle response and throttle position.

Some guys like to wait longer for railing the motor out but bottom line to me is no immediate catastrophic failure and then settle those rings. It doesn't take long

[AJK]

As for tuning the carbs and breaking in the new engine I would make sure the carbs have a good bench synch,should be close enough to run pretty well. Adjust the idle with the knob and go put some miles on it and give it a proper break in by varying the speeds and loads. After a good break in then I would go back and change the oil then fine tune the carbs. Personally I would not want to be running a super fresh tight engine at idle for a long period right out of the box. Also you will not know how your jetting is doing etc till you get out and run it under a load, totally different than on the center stand.

+1

I agree with ekpent here. Just a good bench sync with all mixture screws set the same and get running it in with some road load & without letting it idle too much. Just get the idle in the ballpark to start with & get the engine loaded up with mild load.
  Dump the oil and filter after 50 to 100kms, then install a new filter & mineral oil. Tune it up after about 100kms, at least by then you have done a lot of wearing in.  Keep running mineral oil until about 2000kms, then put in whatever you like.