Throttle Sync Yet Again

Many of you would have seen my previous threads on this. After the last attempt the fuel range until the light came on went up to 97 miles.

This got me thinking that my homemade Manometer might be on the large side and not sensitve enough. I made up another one, this time using 5mm ID polypipe, about 3 feet in length. This did show an imbalance and I adjusted the throttle sync accordingly. This time I spent even longer fine adjusting it, blipping the throttle and then rechecking the balance. Finally when I was happy I adjusted the TPS sensor again and got it kicking in between 1400 and 1500 revs.

Since doing this I have noticed that I can easily cruise at around 30 to 40 mph in a higher gear than normal. I have also noticed that there in a very noticable increase in the induction roar on the front cylinder at low revs when opening the throttle.

It's to early to tell if the range has been improved further as I was part way through a tank of fuel. I have just filled up tonight, so here's hoping.

A word of warning about making a small oil based manometer, when they are this small, if the balance is off by some way, the engine can suck up the oil and lead to a hydraulic lock, killing the engine. You have been warned.

Tim.

Ok, today I found out I was a bit of a muppet, thinking that the increased induction roar was due to an adjustment of the throttle sync. I was getting a bit concerned by the extra noise.

It turns out that the air box had slipped off the rear throttle body after re-fitting at the weekend.

So I thought OK lets check the sync again, and guess what? It was out again. Not by much this time.

It makes me think that there is an air leak somewhere, but everything appears to be fitted OK.

Anyway, I'll see how things go over the next couple of tanks of fuel.

Fingers crossed.

Tim.

[yorkie_chris]

Did you not notice the leanness? I once forgot to tighten one up and it was horrible

Originally Posted by yorkie_chris

Did you not notice the leanness? I once forgot to tighten one up and it was horrible

Funnily enough yes. When I first heard it I thougth, that sounds like a carb that is running too lean. I did think it a bit strange that the amount of noise difference would be caused by throttle sync alone. Especially when you factor in that the total adjustment was about 1/5th of the turn of a screw!

Tim.

[yorkie_chris]

I mean from the airbox boot being loose, leanness gives popping and banging and hesitation and stuff. The noise from the carbs/TB's is just induction roar like you get from an open filter.

Originally Posted by yorkie_chris

I mean from the airbox boot being loose, leanness gives popping and banging and hesitation and stuff. The noise from the carbs/TB's is just induction roar like you get from an open filter.

Not so, when a carb runs lean it makes a lot more noise, in induction roar I mean. Years of being a mechanic and tuning Stromberg and SU carbs taught me this.

[yorkie_chris]

I can understand that one, mine seemed to quiet down a little with the right (ish) mains in. All relative I suppose, for me the massive difference in power delivery was the main thing.