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View Full Version : B&S 6.5HP running slow after carb change


artm
05-09-2007, 09:49 PM
Scotts 22" with B&S 6.5HP Intek 121600 model. No speed control on this model, but I added a cable controlled idle to slow it down when needed.

1. Started it up this season and ran fine for 5 minutes, then cut out. Suspected bad gas as another mower with the same gas did the same.

2. Cleaned out carb with auto carb/choke cleaner. Needle fell out in the process.

3. Started up with a new plug and it ran high, uneven and to the point of stalling when mower tipped back and sideways.

4. Replaced entire carb (original part# 694202) with B&S current replacement part# 790120. The replacement has a couple plastic parts but otherwise identical, I assume.

5, Start it up and it runs smooth but seems not as strong, lower rpm's. This model has front wheel drive and the wheels can actually be stopped with little effort going a bit uphill.

Now, I thought the drive wheel may have the dreaded Scotts stripped plastic gear issue but the engine seems to be running low.

Any thoughts appreciated.

Also: I may have lost a spring controlling the carb throttle (butterfly). Moving the cable does nothing but slightly move the long spring toward and awayfrom the engine. It does not move back the long rod attached to the butterfly, so it stays fully open. I only have one such spring. Am I missing another? It worked before (last season). this isn't a big deal as I only use the mower at full speed almost always but I'd like to solve this nuisance of a problem.

khouse
05-09-2007, 10:58 PM
Recheck you governor linkages.

artm
05-10-2007, 10:44 AM
Linkage is set to butterfly wide open.

Question: going back to the old carb, would dropping the needle cause it to provide uneven fuel? That is, does the needle need to be in its exact position before removal? I have read that the needle shuold not be dropped when cleaning the carb. Perhaps it has "formed" the seat to its shape and changing it leads to fuel getting past the seat unevenly?

Also, the local mower mechanic told me (after the fact) that I should not be cleaning carbs with carb cleaner but mineral spirits, to avoid damaging seals. True?

Ironic
05-10-2007, 11:26 AM
aerosol carb cleaners are fine.
your local mechanic was probably referring to the type of carb cleaner that comes in a bucket, with a tray for dipping/soaking parts. That stuff will eat all the seals for sure.

Bill Kapaun
05-10-2007, 03:53 PM
Just a shot in the dark here-
Are the governor springs the same? (same color?)
What happens if you swap the Main Jet?

Go to the Briggs site and download the parts manual. It'll list the parts and you can try to see if you are missing something.