Pilot jets

[Retrosteve]

Just thought i would mention that although i have stripped the carbs cleaned and rebuilt them with new seals its been a learning curve and something that i did not know or overlooked in the tutorials on here .
Cleaning every orifice is obviously key which i thought id done . However after looking at a number of ytube videos i did not realise that the pilot jets have a pin hole in the bottom that is notorious for getting blocked . This has been the problem with my GS850G from the start . After soaking the jets in carb cleaner for days and using a single wire from a wire brush i cleared the fine hole in the bottom of all the jets . They were totally blocked solid in the bottom fine holes but clear in the side holes .
Was there ever an upgrade on these jets to stop the blockages or is it just normal for them to become clogged after so many miles ?

[zed1015]

There is no upgrade.
Providing the bike is run regularly and the tank and fuel lines are free from debris etc they rarely give any trouble.
Occasionally one may get a partial blockage which usually clears on the run but for all four to become blocked is nearly always the result of the carbs being laid up for a long period of time.

[Nessism]

Screenshot 2024-11-03 040822.png

https://gsarchive.bwringer.com/mtsac/~cliff/storage/gs/Mikuni_BS-CV_Carburetor_Rebuild_Tutorial.pdf

[Retrosteve]

When i got the bike the carbs were not on the bike so assuming these were off a long time or even off another bike that had stood for years . Lesson learnt for the future but at least im up to scratch on total carb rebuilds .
Thanks to all

[Syd]

Was there any noticeable change in performance after cleaning those jets?

[Retrosteve]

Was there any noticeable change in performance after cleaning those jets?

Im going to put the bike together later in the week so will update you Since owning this bike ive had to re wire everything from scratch then rebuild the carbs fully a few times without success .
Clearing these blocked pilot jets will be the last job hopefully and get the bike running .

[Nessism]

Was there any noticeable change in performance after cleaning those jets?

With the pilot jets plugged, the bike will run like garbage.

[Retrosteve]

Im really struggling with these carbs . Every orifice was cleaned and blown out with air , new seals throughout and still it will only run on choke . All i can think of is those tiny holes in the end of the pilot jets have blocked again ? Any other ideas greatly received ?

[Big T]

Well, logic leads one to the fact that the carbs are not clean, otherwise your bike would be idling and running.

Did you follow the carb cleaning tutorial?

[Retrosteve]

Well, logic leads one to the fact that the carbs are not clean, otherwise your bike would be idling and running.

Did you follow the carb cleaning tutorial?

Oh yes followed the tutorial exactly . All 4 carbs were separated and new seals on everything . Ive got them off again and checked it all and nothing is blocked or wrong . The only thing that was a bit suspect to me was that when putting the float bowls back on there was some resistance , maybe hanging up on the pilot jet bungs and could be dislodging them leaving them open but will check those today .

[Rijko]

this may be a suggestion easy to dismiss ... but have seen a number of float bowl gaskets recently that are too large on the float sides.
Rubbing the floats, preventing movement.
So one carb would starve, while the next carb would be stuck in float needle open position.
Are you sure the floats are moving freely ?

side note chuck hahn could this be a cause for your plugs fouling ?

[Retrosteve]

this may be a suggestion easy to dismiss ... but have seen a number of float bowl gaskets recently that are too large on the float sides.
Rubbing the floats, preventing movement.
So one carb would starve, while the next carb would be stuck in float needle open position.
Are you sure the floats are moving freely ?

side note chuck hahn could this be a cause for your plugs fouling ?

Hi your theory about the gaskets was correct . 2 of the 4 were rubbing . Will test to see if this helps .
One thing i notice was that the rubber bungs over the pilot jets where different hights than the other 2 . Maybe not sealing correctly once the bowls are put back on ?
Have ordered some new bungs .

[Retrosteve]

Well once i put the carbs back on , all 4 started to flood , the float hights were spot on . The passageways were all clear , the floats moved up and down freely . New seals on everything so im taking them off again .I dont get defeated easily but patience is running thin on this one . No fuel was getting to number 1 and 2 even though the float chambers were flooded . Amazingly the bike tried to run on number 3 and 4 . But why no fuel is getting to 1 and 2 has me stumped

[dgates1]

Plugged main jets? I think the pilot circuit pulls fuel up through the main jet to the bottom side of the pilot plug. Do they fire with the choke on? Or your needle valves are sticking just a little and don't allow the bowls to fill back up when running? I had to take my carbs back off to clean the needle valves again when I was getting cold cylinders.

[Rijko]

i'd focus on the flooding first.

Only 1 cause for that : the float needles do not shut off for whatever reason.
Floats not moving, float needles stuck, floats at wrong height, something like that.

You have replaced the o-rings between inlet rubbers and head ?