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Peugeot Speedfight 2 AC - - Converted to LC 70ccm, - boils water.

rsv6 12429 19
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Why does my converted Peugeot Speedfight 2 LC 70cc overheat and boil coolant after a few kilometers, and what should I check first?

90°C is normal, so the problem is more likely a cooling-system fault than the 70cc cylinder itself [#16641660][#16641341] First check that the water pump actually has a working impeller/rotor and that the system is bled properly, because these Peugeot pumps are known to fail and lose circulation when the blades are damaged or missing [#16642433][#16641341][#16640900] Also verify that the thermostat opens at about 65°C and that the radiator has enough airflow or a fan if your setup needs one [#16641341][#16640900] If the hoses still swell or burst, suspect combustion pressure from a blown or poorly seated head gasket rather than just coolant temperature [#16641710][#16660268] Use proper coolant instead of plain water, since water does not lubricate the seal and can worsen pump wear [#16645869]
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  • #1 16640607
    rsv6
    Level 13  
    Posts: 1713
    Rate: 282
    Hello everyone.
    I started to replace and convert the engine of the Peugeot Speedfight 2 AC water-cooled scooter to the liquid-cooled LC version.

    I bought a cylinder, piston and 70cc PowerForce heads.
    Cooler, pump, thermostat, temperature sensor and temperature indicator.

    Original carburetor GURTNER FRANCE on the carburetor says 12/12 and the output to the engine is 17mm The nozzle was original 72 I also had a new 60 which I drilled with a 0.8 drill

    I mounted everything scooter that flies like a rocket without comparison to 50 air-cooled.

    Initially, I drove around the yard with no problem. Now I drove 3km and here the uphill stairs have already started ..: c The temperature has risen so that the pressure of the hose bursts, as it turned out the plug did not have a pressure valve, it had, but was not drilled ..; c

    Now I do not know where to look for the problem, the cooler is hot, I put an electronic temperature sensor and it reaches 90 degrees. The hoses are all open, I turned the thermostat because I thought it might be blocked, but it's still lame ..

    The pump from what I can see is pumping since the cooler is hot and the boiling of the water has unsealed water on the o-ring when it heats up.

    I do not know if the cooler is not working or looking for a problem in something else.

    In the previous Air-Cooled version, the engine was also overheating, so that the spark plug stopped giving a spark. It turned out that the stub pipe limiting the amount of air in front of the filter is missing. I put a 20cm long hose there with an elbow at the end and the problem disappeared with overheating and the scooter never overheated so that it went out.
    After the modification, I pulled out the tube and changed the nozzle to 80 t and drilled 60 with 0.8 drill because there was no such in the store. Thinking that maybe he was overheating because there was not enough fuel ..

    Please help!

    Should I put back the 72 nozzles as in 50ccm and this tube ??

    Peugeot Speedfight 2 AC - - Converted to LC 70ccm, - boils water.

    Added after 1 [hours] 26 [minutes]:

    Take a look at the color of the candle ??
    Peugeot Speedfight 2 AC - - Converted to LC 70ccm, - boils water.

    Added after 49 [seconds]:

    Peugeot Speedfight 2 AC - - Converted to LC 70ccm, - boils water.

    Added after 3 [minutes]:

    Peugeot Speedfight 2 AC - - Converted to LC 70ccm, - boils water. Peugeot Speedfight 2 AC - - Converted to LC 70ccm, - boils water.
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  • #2 16640900
    Staszek49
    Level 35  
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    Buddy, I either missed it, or you didn't say - do you have a fan behind the radiator. The radiator is usually hidden behind an openwork diaphragm (dummy) so that air reaches it while driving. I suppose your converted vehicle may have a "top" radiator and no fan. Check fluid pump that impeller has not come off. Bleed the cooling system and maintain proper coolant condition.
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  • #3 16640964
    rsv6
    Level 13  
    Posts: 1713
    Rate: 282
    There is no fan in the original version .. I think I will buy a bigger cooler with a fan from 125cc. Second thing is the pump doing a lot of pressure ?? tz the hose should expand as it squeezes with fingers after adding gas ??

    There is a pump regeneration instruction on the Internet:
    http://forum.mieloch.pl/jak-naprawic-pompe-wody-t62003.html

    The question is whether this plastic is cut next to what is the pump block or the plastic .. What kind of glue to stick it?
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  • #4 16641341
    BANANvanDYK
    Level 42  
    Posts: 7621
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    Did you have a vented system (air vent on the head)?
    These Peugeots have faulty liquid pumps. They often leak, and as they cannot be dismantled (glued), only replacement with a new one is possible. The drive is not twisted?
    Check that the thermostat starts opening at 65 ° C.
    There was no blowout of the head gasket?
    Cooler not muddy, has proper cooling air flow?
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  • #5 16641561
    rsv6
    Level 13  
    Posts: 1713
    Rate: 282
    The new cylinder gasket is intact. I'll try to cut the pump open. However, the cooler is 90 degrees, I think it does not work
  • #6 16641660
    goldwinger
    VIP Meritorious for electroda.pl  
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    And since when is 90 ° C a problem?
    The second thing is water in the system
  • #7 16641710
    andrzej20001
    Level 43  
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    90 degrees is normal temperature. How the hose burst was the pressure caused by the blow from the combustion chamber. The liquid can also be poured in anhydrous. Robust but if despite the 90 degrees. the hoses swell, I put the gasket on.
  • #8 16642433
    rsv6
    Level 13  
    Posts: 1713
    Rate: 282
    I take the pump apart and there is no rotor there ... How is it possible that the radiator has 90 degrees if the pump does not pump because there are no flakes?

    Do you know where to buy a pump that will have a non-plastic impeller?
  • #9 16642878
    BANANvanDYK
    Level 42  
    Posts: 7621
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    Then you have to look for a racing product ... Recently I was looking for something, I came across pump replacements (plastic) for PLN 100. I suspect you won't find aluminum anywhere.
  • #10 16643078
    rsv6
    Level 13  
    Posts: 1713
    Rate: 282
    BANANvanDYK wrote:
    Then you have to look for a racing product ... Recently I was looking for something, I came across pump replacements (plastic) for PLN 100. I suspect you won't find aluminum anywhere.


    Yeah racing ^^ heh the paper will accept all the nonsense and all the same chinszczyzna at auctions ...

    Is there a dismountable metal pump for speedfight?

    What if I put a pump to support the water circulation in cars?
    Peugeot Speedfight 2 AC - - Converted to LC 70ccm, - boils water.
  • #11 16643141
    Staszek49
    Level 35  
    Posts: 2421
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    Rate: 1138
    Such a pump will work. The problem may be the size of the nozzles and the need for constant power supply from the battery, which may "not work out". This "patent" will have an effect on the appearance of the vehicle.
  • #12 16643225
    rsv6
    Level 13  
    Posts: 1713
    Rate: 282
    It will not be visible under the plastic. Hmmm .. What about an ordinary metal pump?

    Added after 9 [hours] 23 [minutes]:

    Nothing to buy a new Chinese pump .. And some kind of borygo or petrygo liquid will have a higher boiling point. I wonder if the water did not break this pump, high pressure and no vent in the plug?
  • #13 16645869
    BANANvanDYK
    Level 42  
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    This electric pump has two disadvantages. First, it gets electricity that the alternator does not generate much. Secondly, the limited working time due to the durability of the brushes in the electric motor (a better solution is a modern pump with a brushless motor - but even a stimulant will be expensive).
    If you use a normal pump, it is mandatory to use coolant - water does not lubricate the sealant. The type of fluid is practically irrelevant.
    How can you get the sealant from the original pump. I wonder if they have introduced something deliberate there that these pumps are failing. You may have bought the engine already with an overheating defect caused by damaged blades (the only question is how did this damage happen). The increase in pressure damaged the seal in the pump.
  • #14 16646055
    rsv6
    Level 13  
    Posts: 1713
    Rate: 282
    BANANvanDYK wrote:
    This electric pump has two disadvantages. First, it gets electricity that the alternator does not generate much. Secondly, the limited working time due to the durability of the brushes in the electric motor (a better solution is a modern pump with a brushless motor - but even a stimulant will be expensive).
    If you use a normal pump, it is mandatory to use coolant - water does not lubricate the sealant. The type of fluid is practically irrelevant.
    How can you get the sealant from the original pump. I wonder if they have introduced something deliberate there that these pumps are failing. You may have bought the engine already with an overheating defect caused by damaged blades (the only question is how did this damage happen). The increase in pressure damaged the seal in the pump.


    Have you read the topic though? The cylinder is new, it is like overheating defect on the old cylinder- AC now is new 70cc- LC
    Rather, I could buy a damaged pump ... For a while the water was boiling and maybe the pressure blew up the blades
    I just don't know how, but since the pressure of the hose burst it, let's say it was possible .. Amazing. Not why the plugs do not have a vent ...

    If I knew that these pumps are so defective, I would buy a new one right away. I had not dealt with the pump before, only the fan was there. And someone thought to put a pump from Piaggio? There it is probably metal and much better.
  • #15 16649197
    rsv6
    Level 13  
    Posts: 1713
    Rate: 282
    Continue the same after changing the pump. Probably because I overheated it a few times and lost some power ... I bought coolers from 125 with a sensor and a fan, now the fan turns on in the middle of the scale and it only sticks out above the plastic because the engine does not fit.

    Added after 6 [hours] 11 [minutes]:

    I don't want to open a new topic for this scooter anymore:
    What should be the compression in 50ccm LC and what in 70ccm LC
    What can a compression sensor be made of. I have the manometer, the cable is the biggest, I have a problem with the cylinder connector instead of a candle ..
  • #16 16658176
    partsbike99
    Level 9  
    Posts: 24
    Rate: 3
    with this cooler, it seems to me that this is not a solution, since the scooter does not have a fan as standard, because it did not need it. At the beginning, I would have knocked out the thermostat and put it back without, because I think he was the culprit. As for the compression gauge, break some old spark plug until the metal collar remains, thread it in the middle and push in the complete car valve. Pour it overnight with good glue (not on the cylinder side) and it's ready ;)
  • #17 16658218
    rsv6
    Level 13  
    Posts: 1713
    Rate: 282
    Or this Power Force WM cylinder from Allegro is some kind of defective ...
  • #18 16660268
    partsbike99
    Level 9  
    Posts: 24
    Rate: 3
    hehe ;) Is it powerforce from motorland or WM from wilmat ?? Powerforce should be walking right now. WM may swell ;) As for the radiator breather - if you did it, it's not good. For circulation to work, you must have the pressure generated by the pump. By making an air vent, the water may have a lower flow velocity. I have the impression that you have a rolled head gasket - the WM cylinder gaskets are tragically made and it's hard to insert them into the head, also it can be this problem
  • #19 16660367
    rsv6
    Level 13  
    Posts: 1713
    Rate: 282
    Where can I buy a good gasket up to 70cc? I bought the cylinder on the Allegro from this guy, the cylinder and the piston seem very well finished, but with the head it is not visible that it is Chinese, because sharp edges are not finished everywhere, castings are not polished at the krucic. : http://allegro.pl/cylinder-power-force-70cc-speedfight-x-race-lc-hit-i6794039212.html
    Please forgive the link, but if there is someone to buy it better to buy a narrative. The question is whether the original head is not too small to 70cc, because the narku is sold without the head.
  • #20 16667452
    partsbike99
    Level 9  
    Posts: 24
    Rate: 3
    first check if it's the seal's fault before you buy it ;) The cylinder is ok ;)
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Topic summary

✨ The discussion revolves around the conversion of a Peugeot Speedfight 2 AC scooter to a liquid-cooled 70cc engine. The user reports overheating issues, with coolant temperatures reaching 90 degrees Celsius and hose bursts due to pressure. Various components were replaced, including the cylinder, piston, and cooling system parts. Participants suggest checking the radiator for airflow, ensuring the water pump is functioning properly, and considering the installation of a fan. The user discovers the water pump lacks a rotor, raising concerns about its effectiveness. Recommendations include exploring aftermarket pumps and ensuring proper coolant use. The conversation also touches on potential issues with gaskets and the quality of aftermarket parts.
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FAQ

TL;DR: Overheating after AC→LC 70 cc swaps often comes from poor coolant flow—thermostat should begin opening at 65 °C, and “These Peugeots have faulty liquid pumps.” Verify the impeller, bleed the system, use a proper pressure cap, and inspect the head gasket. [Elektroda, BANANvanDYK, post #16641341] Why it matters: This FAQ helps Peugeot Speedfight 2 owners diagnose and fix LC-conversion overheating quickly and safely.

Quick Facts

How do I quickly diagnose overheating after converting Speedfight 2 AC to LC 70cc?

Start with flow: confirm the water‑pump impeller is intact and driven. Bleed the system and ensure the head has a vent. Verify the thermostat begins to open near 65 °C. Inspect for head‑gasket leakage and confirm the radiator has unobstructed airflow. [Elektroda, BANANvanDYK, post #16641341]

Is 90b0C too hot for a Speedfight LC?

No. Around 90 °C is normal operating temperature under load. If hoses swell or a hose bursts, suspect combustion gases entering the system, not excessive coolant temperature. Replace the head gasket if swelling continues at normal readings. “90 degrees is normal temperature.” [Elektroda, andrzej20001, post #16641710]

Why did my coolant hose burst after the LC swap?

A burst hose typically means cylinder‑head leakage pressurized the cooling system. That pressure mimics a stuck cap, even at normal 90 °C coolant. Replace the head gasket and re‑torque correctly. Then re‑bleed and recheck for swelling under throttle. [Elektroda, andrzej20001, post #16641710]

Can plain water wreck the Speedfight water pump?

Yes. Water does not lubricate the mechanical seal, accelerating wear and leaks. Always run proper coolant after repairs. The exact brand matters less than having corrosion inhibitors and lubricants. “Use coolant—water does not lubricate the sealant.” [Elektroda, BANANvanDYK, post #16645869]

What if my pump impeller is missing or broken?

Coolant won’t circulate, causing fast overheating and pressure spikes. Replace the pump assembly; many units are sealed and non‑serviceable. Verify drive engagement before final assembly. After replacement, bleed the system and confirm stable temperatures. [Elektroda, rsv6, post #16642433]

Should I add an electric auxiliary water pump?

It can work, but the alternator output is limited and brushed motors wear quickly. A brushless pump lasts longer but costs more. If you install one, fuse it and monitor voltage at idle. “A better solution is a modern pump with a brushless motor.” [Elektroda, BANANvanDYK, post #16645869]

Do I need a radiator fan or a bigger cooler on a converted Speedfight?

Check if your radiator location gets airflow and whether a fan is present. Many conversions relocate or upsize radiators; add a fan when airflow is poor, especially at low speeds or idle. Confirm shrouds and grills aren’t blocking air. [Elektroda, Staszek49, post #16640900]

Should I remove the thermostat to test cooling?

For a quick diagnosis, run temporarily without the thermostat to confirm flow and rule out sticking. If temperatures drop and stabilize, replace the thermostat with a quality unit and verify opening near 65 °C. Restore normal configuration after testing. [Elektroda, partsbike99, post #16658176]

How do I bleed the Speedfight LC cooling system?

  1. Park front‑end high and fill the radiator with coolant.
  2. Open the head’s bleed/vent point until air stops and coolant flows steadily.
  3. Run the engine briefly, top up, close the vent, and recheck levels after cooling. [Elektroda, BANANvanDYK, post #16641341]

My gauge shows 90b0C, but it still overheats. What gives?

If the cap lacks a working pressure valve or the head leaks, the system can over‑pressurize and boil locally. Fit a correct pressure cap, replace any failed pump parts, and retest. The OP observed 90 °C with boiling and a faulty cap. [Elektroda, rsv6, post #16640607]

Are drilled main jets causing lean running and heat?

Drilled jets flow unpredictably and complicate tuning. Replace them with known‑size jets and tune by plug color and response. The thread shows drilled jets alongside heat issues; revert to quality jets before further diagnosis. [Elektroda, rsv6, post #16640607]

Could a poor head gasket cause persistent overheating?

Yes. Low‑quality gaskets can roll during assembly and leak combustion gases. Use better gaskets, inspect fire rings, and retorque heads in sequence. This edge case explains pressure spikes despite normal indicated temperature. [Elektroda, partsbike99, post #16660268]

Is the PowerForce 70cc cylinder to blame here?

Unlikely. Community feedback in the thread indicates the cylinder is fine; focus on sealing, thermostat function, and pump integrity. Verify assembly surfaces and coolant flow before condemning the kit. [Elektroda, partsbike99, post #16667452]

How can I build a compression test adapter for this scooter?

Use an old spark plug shell: remove the insulator, tap the core, and fit a standard automotive Schrader‑valve hose to your gauge. Seal the non‑cylinder side with fuel‑resistant adhesive. This makes repeatable tests affordable. [Elektroda, partsbike99, post #16658176]

My radiator read 90b0C even when the pump failed—how?

Heat can reach the radiator by convection and limited conduction, but circulation remains inadequate. Expect rapid local boiling, pressure spikes, and uneven hose temperatures. Replace the impeller and re‑bleed to restore proper flow. [Elektroda, rsv6, post #16642433]

When should the cooling fan switch on after adding a larger radiator?

Fan trigger varies by sensor and gauge, often mid‑scale on retrofits. Placement and airflow determine activation timing. If the fan engages mid‑scale and temperature stabilizes, the setup is functioning. Secure clearance under plastics. [Elektroda, rsv6, post #16649197]
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