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Post by wallzip on Jun 24, 2023 16:35:07 GMT -5
Hi all,
I'm a little bit out of search and dont know what to do anymore. The problem is that the engine starts to sputter when i open the throttle fully. When i open the throttle slowly up / smoothly than there is not sputter at all. It only happens with 2/3 to immediate full throttle.
The things i already did:
- Changing the complete ignition
- Changed the standard cdi/bobine to a racing top performances cdi/bobine(coil)
- Changed the squish band from 5.5mm to 6.7mm
- Lowered the main jet stepwise by 2 sizes from 100 to 78
- Started bogging on idle, putted the needle 2 clips lower, solved the bogging problem on idle and 1/3 throttle
- Triedd different bougies
- Checked for air leaks, no leaks found
- Changed the spark plug and cable for a racing NGK C4
So basically i'm done searching and dont know what to look for.
I doubt whether it is the carburetor and whether it is causing the problems. I'm not really familiar with Polini CP carburettors but it seems that it doesn't respond to anything.
I want to replace the carburettor for a dellorto 21mm carburettor but not sure if this will make a difference.
Do you guys any other tips I can try? Thank you.
Setup Piaggio Zip Fast Rider:
- Athena Racing 70cc Air Cooled
- Athena Racing exhaust
- Polini CP 21mm with Polini air filter ''blue box''
- Malossi intake and valves VL13
- Malossi overrange set with 3.8gr rolls, purple torque spring
- Top Performances racing cdi and coil
- Standard ignition
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Post by jackrides on Jun 25, 2023 12:53:24 GMT -5
Focus on carburation. First, put your needle clip in a lower slot, raising the needle. See what the response is.
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Post by wallzip on Jun 26, 2023 3:58:03 GMT -5
Focus on carburation. First, put your needle clip in a lower slot, raising the needle. See what the response is. I already did that by one and than 2. It doesnt make a difference. |
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Post by jackrides on Jun 26, 2023 9:11:22 GMT -5
I do not know Polini carbs. I did have a similar issue with a Mikuni. They have a small air port in the front going to the needle jet. Purpose is to begin the atomization process in the needle jet (they call it an emulsion tube). During my second disassembly of the beast, I removed the slide, then the main jet and pushed out the needle jet and cleaned the inside of the body encasing the needle jet and air inlet to it. I got a gift of dried old fuel flake. Afterwards, ran great. I'll not bother you further about carbs. Good luck.
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Post by RyanWiltshire on Jul 1, 2023 2:59:43 GMT -5
did you manage to fix this issue? if you did, what did you try?
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Post by wallzip on Jul 1, 2023 5:25:37 GMT -5
did you manage to fix this issue? if you did, what did you try? Nope, didnt work on it because I've already gone through all possible causes and so I don't know where to look anymore. I'm still planning to replace the Polini CP 21 for a Dellorto 21mm carburator. |
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Post by RyanWiltshire on Jul 1, 2023 9:20:07 GMT -5
honestly, the one thing you haven't done is a carb swap? friend had a issue for ages since he rebuilt it with spluttering and it was carb related, but he swap to a identical carb and it fixed the issue, quite common man. give it a try. plus Dellortos are probably the best to tune. I have to take my aerox to pmtuning to go on the dyno due to struggling with my stage6 r/t 21mm racing carb. good luck and keep us updated  |
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Post by jackrides on Jul 1, 2023 14:28:18 GMT -5
Try a carb with an accelerator pump.
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Post by classacted on Jul 1, 2023 20:13:48 GMT -5
I always like to have at least one spare carb that works great ready to go at all times. that way, you can change the carb and know whether the carb is the issue with certainty.
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Post by wallzip on Jul 22, 2023 11:50:30 GMT -5
honestly, the one thing you haven't done is a carb swap? friend had a issue for ages since he rebuilt it with spluttering and it was carb related, but he swap to a identical carb and it fixed the issue, quite common man. give it a try. plus Dellortos are probably the best to tune. I have to take my aerox to pmtuning to go on the dyno due to struggling with my stage6 r/t 21mm racing carb. good luck and keep us updated Installed a brandnew 19mm Dellorto carburator with a Malossi E14 filter but unfortunately it didnt solve the issue. The exact same problem still excist pfff 😔 |
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Post by classacted on Jul 22, 2023 14:53:47 GMT -5
darn.
you change alot of things that I would never change. I always stick with stock, so I can't question any of the parts you use that are not.
when is the last time you looked at the spark plug? did a compression test? checked the timing chain that it meshes with the gear properly? inspected the valves?
checked for water in the gas?
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Post by wallzip on Jul 22, 2023 17:20:31 GMT -5
darn. you change alot of things that I would never change. I always stick with stock, so I can't question any of the parts you use that are not. when is the last time you looked at the spark plug? did a compression test? checked the timing chain that it meshes with the gear properly? inspected the valves? checked for water in the gas? Spark plug is from last year and i have a number 9 in it. The plug is maybe 50km's old. Last year i also tried different numbers but it didnt help either. Its a 2 stroke so no timing chain. I also did check the valves for cracks or other things but nothing visible. No airleaks. No water. Also tried different fuel mix with oil but didnt help either. I can put the carburation aside now and dont believe that it causes the problems. Despite changing the ignition for a new one and mounted a Top Performances CDI, i think that there is still a ignition issue. After opening the throttle smoothly the RPM builds up and at a certain rpm it starts the sputter. I think its above the 10k RPM where the trouble starts. The Top Performances CDI should be able to work fine above the 10k RPM but i'm not sure now.. |
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Post by classacted on Jul 22, 2023 18:02:30 GMT -5
how many miles on the piston and cylinder? has anyone ever removed carbon buildup? you could have a pre-ignition condition where the carbon is glowing hot and ignites the fuel prematurely.
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Post by wallzip on Jul 22, 2023 18:38:12 GMT -5
how many miles on the piston and cylinder? has anyone ever removed carbon buildup? you could have a pre-ignition condition where the carbon is glowing hot and ignites the fuel prematurely. I think about 100 km? Its not very old or a lot used for riding (only tested a lot). A few km ago i demounted the cylinder to check it and there was no carbon build up at all. Piston head was nice clear. The strange thing is despite trying different main jets etc. my sparkplug stays light grey which is not really a good sign of ignition. I'm increasingly doubting whether the CDI can handle the RPMs. It is a fixed CDI (yellow one from Top Performances) Would a variable CDI work better? I read that these are much more suitable for engines running above 10k rpm but i'm not sure. |
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Post by RyanWiltshire on Jul 23, 2023 7:04:11 GMT -5
how many miles on the piston and cylinder? has anyone ever removed carbon buildup? you could have a pre-ignition condition where the carbon is glowing hot and ignites the fuel prematurely. I think about 100 km? Its not very old or a lot used for riding (only tested a lot). A few km ago i demounted the cylinder to check it and there was no carbon build up at all. Piston head was nice clear. The strange thing is despite trying different main jets etc. my sparkplug stays light grey which is not really a good sign of ignition. I'm increasingly doubting whether the CDI can handle the RPMs. It is a fixed CDI (yellow one from Top Performances) Would a variable CDI work better? I read that these are much more suitable for engines running above 10k rpm but i'm not sure. I just read what you have already tried and I see you have tried most things. have you check the piston/ring etc? when you changed the CDI, was the bike working fine before or when you changed it, it started to do the spluttering? |
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