I have recently switched from a Rotax Max to an IAME X30 engine, and I was wondering if someone could help me out with the carburettor’s maintenance. The engine currently has 5 hours on it, and from my research at this point the carburettor is due for a rebuild.
I purchased a pop off gauge as well as a full and a half rebuild kit, and when testing (connected the gauge directly to the fuel strainer) the carb popped off at 9psi, and then held steadily at 7psi. From what I’ve seen online, this means that the carb is still in a good condition and does not need a rebuild yet.
This brings me to my question, at which point should I fit in the half rebuild kit, and at which point should I fit in the full rebuild kit? The Tillotson guide mentions the following, however I’m not sure what leaking and sealing exactly refer to.
If it is sealing well, it is necessary to fit a DG kit only; however if it is leaking or not sealing, it is advised to fit an RK kit.
There are also some other things that I am unsure of:
- Is there any reason why I should test the pop-off pressure with the carburettor dismantled using the adapter, as opposed to testing by just connecting the pop-off gauge to the fuel strainer?
- Should I replace the spring at some point, or should I change it only to alter the pop-off pressure? With regards to the latter, from what I’ve read changing the pop-off pressure seems to richen or lean the carburation throughout both the low and high jet. If so, what is the point of altering the pop-off when you can achieve the same thing by tuning both jets?
- Apart from the things I mentioned, is there anything else to keep in mind to keep the carb performing optimally?
Thanks in advance for any help!
Pop-off pressure is not the only determining factor in rebuilding a carb. The amount of usage or the length of time between carb rebuilds will have more influence. If the carb does not hold pressure, could be a sign of a worn or damaged needle and seat. With time and usage, the pump diaphragm loses some of its elasticity. We have a short racing season, so I will replace the needle and seat once a year. As for the diaphragm, after every couple of race weekends works.
Thanks for your reply! I will open up the carb this weekend and have a look at the state of the diaphragm. If it looks worn, I’ll fit in the half repair kit.
If you are not aware of your carbs history, may just want to install the gasket set to have a base line on the carb. There are several videos online on rebuilding the carb. Of coarse, I couldn’t find the video I wanted, but these will give you a start. Good luck.
I rebuilt my hw27a and may have mixed up the hi/lo screws. Anybody know which taper is what? Is it longer is high and short taper lo, or is it vice versa?
Looks like the longer one is the high speed…
Source: Tillotson-HW-27A-Homologation_Fiche.pdf (1.1 MB)
Yes, that’s the same thing I thought when I saw that pick but was hoping someone could confirm. I never trust myself, especially my eyes
Very weird, but that picture from the Tillotson fiche is wrong; the longer tapered needle is the low speed needle. The part numbers are correct, the pictures are just swapped. It’s correct on every other fiche I’ve ever seen.
Wow. Ok I better check my history and see where I got it from
What do you guys do with your carbs after a racing day maintenance wise?
How do you empty any fuel in the carb after a race?
Do you use any products to keep the diaphragms in good working condition?
Bump… 20 characters.
Any info is much appreciated. Thanks
I usually leave the fuel in there, rationale being that it’s possibly better to have fuel in there vs air which can lead to oxidation\reaction. Assuming it’s going to be in there for a short amount of time…
Team take the tank off so the kart can be stored vertical is all.
Exactly. Practice session is never far away