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Post Info TOPIC: Am I running lean?

Senior Member

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Posts: 107
Am I running lean?

As far as I am aware, my TTR pulls like a train right through the rev range. Well, a small train. But there is a slight bog between 1/4 and 1/2 throttle, but only if held there for a sustained period, i.e. cruising down a long straight 30MPH road, then when you go to take off when the speed limit increases, a tiny hesitation then continues to rev as normal. It pops a tiny bit on deceleration, from about 1/2 to 3/4 revs down, but from WOT no popping.

I couldn't tell you what jet sizes are in there at the moment, but I know the needle was on the middle clip. Mods wise, a 263 piston, a DG-O silencer, a previous owner removed the snorkel and cut a hole in the top of the air-box about the size of your fist, I covered it in a mesh. I have a twin-air air filter and I think that's about it. I'm in England at about sea level.

The problem is, I took the engine apart and found my valves looking like this:

The last time I went into the engine, the valves looked OK, which was only about 7,000 KMS prior to that. So something has changed, and that is the fact that I have bored her out a bit and fitted an aftermarket silencer, that does no silencing. The spark plug also showed signs of running lean, it was white. I have also been running the bike on super-unleaded, it may be my imagination, but I seem to get better fuel economy with the 99 Octane stuff.confuse

Any help from carb gods would be much appreciated. I haven't rode the bike since November, so I'm just trying to go off memory what it was like, and my shocks still being refurbed and the engine is still in bits, so I can't take it for a run to check it out.



Adam. 1993 Open Enduro: 14/48 Gearing, Uncorked, Twin-Air Filter, Snorkel Removed, 263cc Piston, Ported and Polished Head, Shorty Header, DG-O Silencer(Loudener!), 140 Mikuni Main, Standard Pilot, Bottom Needle Clip (Still A Touch Lean)

Senior Member

Status: Offline
Posts: 116

Based off of your discription, I seems like it's only lean in the mid (needle) circuit. Maybe just lift the needle up to see if it helps?

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