26cc carb

[paul hughes]

I am in need of some technical advice please I have a 25cc engine which was running fine until the carb started to play up, although i have cleaned it and changed all the gaskets and membrains it has made no differance. As a test i fitted a carb from a zenoah 38 to the engine and although the linkages don't match up the engine did run faultlessly. It did seem a little down on power in the air so i have been trying to find a replacement for the origanal carb which is a walbro wt719. I have not been able to track down a an exact replacement however i have found a carb for a 26cc engine which looks identical in every way exept the BORE. The origanal has a 15 mm bore but the replacement is only 13mm.
Will this make any differance to the performance, i appologise if it seems like a stupid question.

[Tony Collins 1073]

sorry wrong post

[Tony Collins 1073]

Hi Paul, The slightly smaller carb venturi will need careful retuning - you may possibly get a bit less power. As far as the other carb is concerned, this has cropped before and I did make some suggestions together with a link to go to.
You may have changed the diaphragm etc but have you pressure blown the low and high jets. By pressure blown I mean removing the needles one at a time and blasting air through the needle valve hole. T o do this properly you must have a good seal over the hole. I find a very good way is to use a bicycle pump with something like a football blow up connector. Fit a piece of fuel tubing on the end and make sure the tubing is dead square to make a good seal over the hole. You may need another pair of hands to do this properly as you need a really quick pump to be effective. You can check the result by squirting WD 40 with its plastic tube stuck well into the hole. A quick squirt and see if it is coming out of the main jet at the front of the carb and the low jet at the rear, remove needles separately
Good luck. Here is the link.


http://www.wind-drifter.com/technical/wg8walbro.php

How did I manage to quote myself? Oh well you can't win ém all.

[Barry Bennett]

The difference between 13mm dia and 15mm may seem small but the area difference is 25% 15mm dia is 25%larger in area than 13mmdia.
You are probably aware of this Paul.
Barry

[paul hughes]

Hi, back on this again! can anyone tell me the bore of a Wt645 carb as found on a zenoah 26. thanks

[Tony Collins 1073]

Hi Paul. 15.88mm bore, 12.7mm venturi.