Carb hesitates/coughs at the 4500 - 5000

Riceburner · 07-29-2015, 04:48 AM

Ok folks please help. I posted this in the carbureted version mods & repairs but haven't heard from any of you smart people.

I have the Zongchen / MotorstarZ250R, Philippine version, it's carb powered and mine has had issues from day one. I had the hesitation issues at first from 3500 to 5000 RPM, several trips to the dealer and it went from bad to worse to un-ride-able, with Km per liter down to 13 KPL, (really), since new I have only been getting max 19.6 KPL. Then they got to where it only hesitated/coughed at 4500 to 5000 and 21 KPL.

This happens in all gears and any speed, it's the RPM range, 4500 to 5000.

Thanks to Mororstar's head mechanic in Manila he posted a fix on Facebook and on Saturday 25th the local shop mechanic performed the adjustments, I took a print out for him to read and see. This is his instructions:

Eric Dela Cruz
July 19 at 4:03am

1. Remove the white plastic washer of the carburator jet needle (as shown on attached pics above) to set the fuel in lean condition 2. Set or place the circlip at the topmost notch 3. Adjust the air screw at the 3 full turn clockwise

The bike was much better, felt perfect and I was happy on my 35 Km ride home. The next morning going to meet friends for a long ride at about 20 km into it I noticed the same hesitated/coughed at the 4500 - 5000; what???

We went on a 350 KM ride and these guys ride fast, fast for here in Iloilo and Panay road conditions, I'd say we were averaging 80-90 KPH and sections of 120 many times; I hit a top sustained speed (indicated) 145 KPH (90 MPH), that's what I made it too anyway. My average KM per Liter was 25.6 (all indicated as per the stock speedo and Odometer and we know they aren't accurate but close enough for now). I was surprised when I calculated this, thought it would be worse.

The entire trip I had that constant RPM problem and that makes riding very annoying and even possibly dangerous given you can't just turn the throttler and accelerate without hitting that RPM range, just not right.

I did tell the local mechanic that I understand the engine and carb must be hot when adjusting PMS and of course he didn't listen to me, did it all on a cold engine.

I want to like this bike but as of right now I can't say I'd purchase another one or recommend it to my friends. I need to get the carb under control and redo the seat again, terrible seat for me. I know the details can be corrected and I'm sure I will end up enjoying at some time.

So, anybody got other ideas here?

07-29-2015, 04:48 AM	#1
Riceburner Join Date: Jul 2015 Location: Tigbauan, Iloilo City, Panay Island, Philippines Posts: 177	Carb hesitates/coughs at the 4500 - 5000 Ok folks please help. I posted this in the carbureted version mods & repairs but haven't heard from any of you smart people. I have the Zongchen / MotorstarZ250R, Philippine version, it's carb powered and mine has had issues from day one. I had the hesitation issues at first from 3500 to 5000 RPM, several trips to the dealer and it went from bad to worse to un-ride-able, with Km per liter down to 13 KPL, (really), since new I have only been getting max 19.6 KPL. Then they got to where it only hesitated/coughed at 4500 to 5000 and 21 KPL. This happens in all gears and any speed, it's the RPM range, 4500 to 5000. Thanks to Mororstar's head mechanic in Manila he posted a fix on Facebook and on Saturday 25th the local shop mechanic performed the adjustments, I took a print out for him to read and see. This is his instructions: Eric Dela Cruz July 19 at 4:03am 1. Remove the white plastic washer of the carburator jet needle (as shown on attached pics above) to set the fuel in lean condition 2. Set or place the circlip at the topmost notch 3. Adjust the air screw at the 3 full turn clockwise The bike was much better, felt perfect and I was happy on my 35 Km ride home. The next morning going to meet friends for a long ride at about 20 km into it I noticed the same hesitated/coughed at the 4500 - 5000; what??? We went on a 350 KM ride and these guys ride fast, fast for here in Iloilo and Panay road conditions, I'd say we were averaging 80-90 KPH and sections of 120 many times; I hit a top sustained speed (indicated) 145 KPH (90 MPH), that's what I made it too anyway. My average KM per Liter was 25.6 (all indicated as per the stock speedo and Odometer and we know they aren't accurate but close enough for now). I was surprised when I calculated this, thought it would be worse. The entire trip I had that constant RPM problem and that makes riding very annoying and even possibly dangerous given you can't just turn the throttler and accelerate without hitting that RPM range, just not right. I did tell the local mechanic that I understand the engine and carb must be hot when adjusting PMS and of course he didn't listen to me, did it all on a cold engine. I want to like this bike but as of right now I can't say I'd purchase another one or recommend it to my friends. I need to get the carb under control and redo the seat again, terrible seat for me. I know the details can be corrected and I'm sure I will end up enjoying at some time. So, anybody got other ideas here?
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