Bigger carburetor crf50?

[scuba]

I want to put a bigger carby on my crf50 with 88 kit but im not sure wat size would run the best. At the moment i have an 18mm. please help!!!!

 

[rider456]

18mm will run fine on a 88 limo but 20mm would be the best..

 

[scuba]

yeah, i was thinking 20mm, i might buy the keihin 20mm at oz50 just wondering how good they are?

 

[Cactus Jack]

Be careful of carb sizes ... a genuine 20 mm Keihin measures 22 mm at the rear ... a genuine 22 mm Keihin measure 24 mm at the rear ... A carb that measures 20 mm at the rear will be an 18 mm job ...

An 88 cc engine should handle a genuine 22 mm Keihin (24 mm at the rear) no probs since I've run them on XR75's ranging from 76 cc up to 96 cc without any dramas ...

An XR80 20 mm carb (22 mm at the rear) should work spot on but will make less top end power than the 22 ...

 

[Hillz]

yer i got a CRF70 carb on mine, think thats 20mm

 

[Cactus Jack]

Here's a PC-20 XR80 carb :

Here's a genuine 22 Keihin SL/XL100/125 carb :

22 Keihin next to a 20 Keihin :

 

[scuba]

jeepers! your right, i think ill buy the keihin 20mm (22mm rear) sounds like the best option

 

[rider456]

yeah if u have stock head dont go over 20mm but yeah 22mm on race head will be good

 

[rider456]

yer i got a CRF70 carb on mine, think thats 20mm

crf70 carb is 17mm...

 

[scuba]

Dang it, i have a stock head

 

[rider456]

keihin pc 20mm it is..

 

[Cactus Jack]

50's shops BS the sizes of their Keihin copy carbs ... they say a carb that's 20 mm out the rear is a 20 mm carb and one that's 24 mm out the rear is a 24 mm carb ... They're only those sizes IF the venturi is 24 or 22 mm round thru the slide area ... if they're oval (which they are) ... they're smaller in actual airflow than the rear measurement ... LOL ...

Some ebay sellers BS Keihin 22's as 24 mm carbs too ... based on the measurement at the rear ... I questioned one guy in the US and he wouldn't show me the top of the carb ... but I could see that he'd ground or filed the 22 raised number casting off ...

 

[Cactus Jack]

Everyone put a 22 mm Keihin on 80 cc bored XR75's ... Knowing the difference they make over the stock 20 mm carb (22 mm out of the rear) ... I couldn't see a CRF88 having much power with a 20 ...


22 Keihin next to a 20 Keihin :