Rovan Baja Bogging under throttle

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, and others.

Taken

Well-Known Member
Build Thread Contributor
Messages
87
Location
Area 51
I went to run my baja and it is bogging under throttle. I think it might be an issue with the fuel because I had to manually inject fuel into the cylinder through the spark plug hole with a syringe to get it to fire up. Once it starts it idles fine but if I go more than about 1/2 throttle it just bogs. I tried tuning the carb richer on the low speed needle but it didn't do much.

Video of it bogging:
 
I would start with reset on both high and low needle settings as it is always good to start with a default point. What some have stated about the throttle plate position, the low needle setting is only in effect for 1/3 of the plate travel and past that is where the high flow takes over. I do not believe the low needle jet shuts off at this point and would assume that both jets are flowing fuel. This would make me think your high flow needle setting is either too rich or probably too lean.

Here is the boiler plate written note on needle settings that came with my King Motor 30.5cc engine. KM and Rovan are basically the same but may have different carburetors on the same size engine ROFUN clone vs Walbro.

General defaults as stated in the Engine instructions that came with my vehicle. (I assume they address the different carbs for each range of engine size).
23cc - 30.5cc: L is 1 1/4 turns out, H is 1 1/2 turns out.
32cc: L is 1 1/4 turns out, H is 1 7/8 turns out.
34cc - 36cc: L is 1 1/4 turns out, H is 2 1/4 turns out.
45cc: L is 1 1/2 turns out, H is 1 5/8 turns out.
 
Well I reset the carb and it doesn't seem to be bogging anymore but I still have to inject fuel into the cylinder for it to start.
Try screwing in the idle stop screw clockwise (throttle plate stop? aka idle speed control) just a bit. It is that large screw below the needle screws that has a chamfered edge that is used to adjust the throttle plate position for idle. That should move the throttle plate enough to keep it open to allow for air/fuel mixture to get in. If idle speed seems a bit high, you can adjust that with the low needle screw by making it a tad richer.

Another trick would be to use the throttle trim on the transmitter to open up the throttle for starting purposes. I used to have to do this for the Nitro engines. Those were always a pain to get started. So far, I never had any issues getting the 2 strokes to fire up (not true, my King motor 30.5 was a dead horse from the start. I think I fixed it by readjusting the ignition coil position. I will find out soon enough once I get the vehicle back together.)
 
Try screwing in the idle stop screw clockwise (throttle plate stop? aka idle speed control) just a bit. It is that large screw below the needle screws that has a chamfered edge that is used to adjust the throttle plate position for idle. That should move the throttle plate enough to keep it open to allow for air/fuel mixture to get in. If idle speed seems a bit high, you can adjust that with the low needle screw by making it a tad richer.

Another trick would be to use the throttle trim on the transmitter to open up the throttle for starting purposes. I used to have to do this for the Nitro engines. Those were always a pain to get started. So far, I never had any issues getting the 2 strokes to fire up (not true, my King motor 30.5 was a dead horse from the start. I think I fixed it by readjusting the ignition coil position. I will find out soon enough once I get the vehicle back together.)
That seems to have fixed the problem. Thanks for saving me some hassle and unnessessary wrenching.
 
I am glad you have a resolve.

I recently got an ESP-Zenoah G340RC engine. It seems they instruct the use of the throttle trim to adjust the throttle position for starting purposes. I always had to do that trick to start Nitro engines. So far, I have not needed to do this with any of the 2 stroke engines I have in my vehicles. Just be careful if you need to do so, you can flood the engine that way if it does not start.
 
Back
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock    No Thanks