Stutter at 3250rpm
- Thread starter cbertozz
- Start date
L
Legs
Guest
Standard ignition?
L
Legs
Guest
If ypu have the standard Bosch ignition fitted, the stagger at around 1300 revs is normal, led to believe that it's caused by the the ignition advance/retard kicking in at those revs. The best way to get around it is to fot any aftermarket system; MotWitt, Sasch or whatever.
The above applies to the 120s, thinks it applies to the 180s as well.
The above applies to the 120s, thinks it applies to the 180s as well.
G
Grant
Guest
Might also be carburation.
Mucky carbs or even jetting transition/taper of the needles.
Mucky carbs or even jetting transition/taper of the needles.
AndyW
Hero member
Legs said:
I think you'll find it's around 2800-3000rpm on the BTZ ignition 180s
Suspect Grant is on the money though as that's roughly where the main jets start to kick in so is likely to be a blocked pilot jet or (as in my own recent experience) an air /vacuum leak on one of the inlet stubs: a can of easy start will diagnose this very quickly..
L
Legs
Guest
My mistake, should be around 3200 rpm for an RGS.
piranha-bro2
Hero member
- Location
- Melbourne
AndyW said:
Won't have anything to do with main jets unless you are over 3/4 throttle and hammering. Pilot jet system definitely at play though, so making sure all the passages are clear is very important.
Laverdalothar
Hero member
- Location
- Germany
Is it new or has it been always there?
New:
-change spark plugs, check spark-plug caps and cables, check you have EITHER caps with resistors OR spark plugs with resistor. not both and not none! Check the plugs on the ignition coils are all sitting tightly on the connectors and no cable is broken or without insulation, touching the frame etc.
-if old Bosch BTZ or HKZ ignition: check Pickups and cables. One of them has a engine-stop-relay, which can also cause issues
-Check there is no issue with the ignition key switch and its cables. Had that before with a cable that was almost falling off...
-check the fuse box so that all fuses sit tightly in their seats and are not corroded (also the connectors...)
-when was the last time the carbs saw some service? check they are clean, no water in the float bowls, float valves are closing and all jets have correct size and are not blocked.
-check setting and try to bring them to factory settings with 1,5 turns out from full in for the mixture screws.
-make sure the choke-plungers do move equally (all three) and that they fully close! There is a small jet reaching into the float bowl for the choke system. The O-ring very often is damaged or not in right position, which enrichens the system...
-Now try to sync them. If the main sliders do have to be positioned at different levels to achieve synchronisation, you inlet-stubs are either cracked, O-Ring is broken or missing or valves need adjustment.
-Check valve clearance. if they are OK and fully close, you might need a compression and maybe even a leak-down-test of the cylinders to see if they really close equally.
-Adjust timing chain tension as well as primary chain tension correctly.
-take the Carbs off the bike and check the inlet stubs and their isolators as well as the O-Rings for damages.
-if the carbs havn't been serviced for an unknown time, it is time now. Take them to someone who has done it before on these carbs, as there are some traps you can fall into (O-Rings that hide behind a tiny washer etc.). Get them ultrasonic cleaned, sliders and housing checked for wear and if OK, install new gaskets and jets and adjust them on the bike again. Don't forget to exchange needle and needle jet, too! Very often forgotten...
Also check the engine mounts are all correctly tightened. If the engine can move around, the slightest issue results in a slight change of revs which can cause also some stuttering.
If this all does not help or if you have done most of the steps above before or the bike always behaved like that, I would change to a modern ignition if not already existing.
HTH and hope, I did not forget to much that would need checking...
New:
-change spark plugs, check spark-plug caps and cables, check you have EITHER caps with resistors OR spark plugs with resistor. not both and not none! Check the plugs on the ignition coils are all sitting tightly on the connectors and no cable is broken or without insulation, touching the frame etc.
-if old Bosch BTZ or HKZ ignition: check Pickups and cables. One of them has a engine-stop-relay, which can also cause issues
-Check there is no issue with the ignition key switch and its cables. Had that before with a cable that was almost falling off...
-check the fuse box so that all fuses sit tightly in their seats and are not corroded (also the connectors...)
-when was the last time the carbs saw some service? check they are clean, no water in the float bowls, float valves are closing and all jets have correct size and are not blocked.
-check setting and try to bring them to factory settings with 1,5 turns out from full in for the mixture screws.
-make sure the choke-plungers do move equally (all three) and that they fully close! There is a small jet reaching into the float bowl for the choke system. The O-ring very often is damaged or not in right position, which enrichens the system...
-Now try to sync them. If the main sliders do have to be positioned at different levels to achieve synchronisation, you inlet-stubs are either cracked, O-Ring is broken or missing or valves need adjustment.
-Check valve clearance. if they are OK and fully close, you might need a compression and maybe even a leak-down-test of the cylinders to see if they really close equally.
-Adjust timing chain tension as well as primary chain tension correctly.
-take the Carbs off the bike and check the inlet stubs and their isolators as well as the O-Rings for damages.
-if the carbs havn't been serviced for an unknown time, it is time now. Take them to someone who has done it before on these carbs, as there are some traps you can fall into (O-Rings that hide behind a tiny washer etc.). Get them ultrasonic cleaned, sliders and housing checked for wear and if OK, install new gaskets and jets and adjust them on the bike again. Don't forget to exchange needle and needle jet, too! Very often forgotten...
Also check the engine mounts are all correctly tightened. If the engine can move around, the slightest issue results in a slight change of revs which can cause also some stuttering.
If this all does not help or if you have done most of the steps above before or the bike always behaved like that, I would change to a modern ignition if not already existing.
HTH and hope, I did not forget to much that would need checking...
Rob
Hero member
- Location
- Midlands, UK
Replace carb slides; needles & needle jets. The latter two wear noticeably at quite low mileage.
Ignition induced stagger is generally an issue on 120 rather than 180 motors with standard ignition due to the latter having two of the three cylinders firing together on the same part of their step advance curve.
Ignition induced stagger is generally an issue on 120 rather than 180 motors with standard ignition due to the latter having two of the three cylinders firing together on the same part of their step advance curve.
Thanks for the feedback and as always the detailed feedback Lothar!
It's a new phenomenon as far as I can remember, dating back to when I ran the bike down at the track. (fuel clogging carbs?).
Anyway, I think its time I worked out carbs work as well as the other gubbins. I will check the electrical stuff first as thats easy and work through from there.
Trying to find the time is the struggle at the moment but given the weather its a good time to be working on the bike.
It's a new phenomenon as far as I can remember, dating back to when I ran the bike down at the track. (fuel clogging carbs?).
Anyway, I think its time I worked out carbs work as well as the other gubbins. I will check the electrical stuff first as thats easy and work through from there.
Trying to find the time is the struggle at the moment but given the weather its a good time to be working on the bike.
D
Davo
Guest
Always keep in mind the maxim:- Most carb problems are electrical (and viccy vercy)
Laverdalothar
Hero member
- Location
- Germany
Rob said:
well - it is a question of the Bosch switching hard from late to early advance at that time. I had it both on the Jota 180? and the SFC before I installed the DMC...