IAME Tillotson HL 394A Carburettor - clean up.
We had the engine on the dyno at Shark and confirmed what someone else had told me - there was a problem with the Tillotson carb.
I like being around seasoned karters, it reminds just how much I don't know. For example: when we were running the Honda a guy told me he could hear a rattle from the front tyres. Sure enough they had become a little loose and had about 1mm left-to-to-right movement. To be successful at this game you need all your senses working nicely. You also need to know what to listen for - and that is where I'm weak.
Someone told me that our carb was not right - he could hear that the engine note was not correct. So I bought a Tillotson carb kit that just had the seals, gasget and "mixers". There is a technical name for the "mixers" but I don't know what it is.
Getting the carb off isn't hard but it is fiddly. Getting a 10mm spanner in to loosen the nuts takes ages. I wonder if there is a ratchet spanner that works from the side ... something to check later.
Once off I removed the 6 screws from top and made a mental note of where everything was as I took out the various seals and bits. I've used carb cleaner before when I stripped and cleaned the carb on the Honda and it is evil stuff. When it says use in a well ventilated area it means outside. Last time I simply opened the garage door. The result was me ending up high as a kite. The stuff melts latex gloves.
This time I did my spraying outside wearing two pairs of latex gloves. I still managed to inhale some of the fumes but not enough to get even light headed. I had put a latex glove on the rear bumper of my van before I started to rest the bits on when I finished spraying as I wanted to air dry them on something clean. Not getting muck, grease and dust in the carb was very much on my mind. I retired inside to make a sandwich while the evil spray evaporated. An air compressor would have been handy here to blow it all dry.
It was now time to re-assemble and I thought about the cleanliness aspect. I was sure the mayonnaise on my hands wouldn't be a good thing so I gave them a good wash. The different bits go back together easily and I soon had it ready to re-attach to the engine. This bit was the most frustrating - trying to get the nuts on was a real faff. The sound a nut makes when it hits an aluminium table can drive a person mad.
Now came the real test - had I done it properly? Would the engine start. The short answer was no, it wouldn't. I pulled the spark plug out to see if it was sparking and it wasn't. Bugger. Then I remembered that it wouldn't spark with out touching some metal so I placed it on the head and pulled the chord - sparks!! Spark plug back in and try again. All the time in the back of my mind a little voice was saying "you should have just left it alone, it worked. Now it's broken and you'll never get it working. Well done you!" Pulling the chord with my left hand and manipulating the throttle with my right didn't come naturally but I fumbled away and gave the chord a pull and bingo! the engine came to life. The only reason it hadn't started before was lack of left and right hand coordination. William is usually there to do the accelerator bit.
According to the Alfono the engine is maxing at 15.5k RPM on the trolley. And this is where I do have a regret. Before starting I should have got a bench mark to see where the engine was maxing. My knowledge of carbs is insufficient to know if the new bits would make a difference to top end revs - but it is something that can be measured before and after and gives me something to take to the engine tuner for a discussion.
Anyway the engine does sound different, the tone of the note seems higher with more treble than before. A kart engine engineer told me that the top learn mix should be set so the engine tops out at 14.4k on the trolley. So this is something I will be concentrating on for the rest of the week.
The next thing I think I need is a carb pressure tester to see where it is popping off. And then I can play with different paddle arm springs to see what difference they make.
I'm not sure if this is a hobby or an addiction.
Author: Jez Caudle. Published: Thursday October 8 2015Tweet