Hope someone can help. I recently replaced a cracked piston, got it all back together, initially ran fine, but as it warmed up, it started bogging and choking at about 1/2 throttle, then 1/4 throttle to just crawling back to the garage. It starts fine and idols fine, but anything past 1/4 throttle now it just chokes and sputters. I have moved the timing chain one sprocket each side of where it originally was, but result was the same. Any suggestions? Thanks in advance.

 

Start at the basics and if you haven't cleaned/rebuilt the carb,eliminate it as the problem along with having a good clean air filter.You can also pull the fuel line from the carb,crank the engine over and you should have a good flow of fuel. Make sure you have the stator plate timed to the case mark. If none of this helps you may want to remove the tensioner, stator plate and reset the cam timing. The lower crank sprocket marks aligns with the case mark on the bottom.This is tdc. Have the cam sprocket index pin dead center of the head and reposition it on the cam. Reinstall the tensioner,set the valves,install the recoil and pull over slowly so the tensioner adjusts slack on the cam chain.

 

Ok, Thank you, I get most of it, except for, "The lower crank sprocket marks aligns with the case mark on the bottom". I think this refers to the smaller of the two pics you sent. Exactly where do I look for this mark, I dont recognise the drawing, and whats the best way to clean the carb? I have a new air filter, the fuel flow is good, and I have a new spark plug. Thanks again.

 

This is just a generic pic on cam timing.The lower crank sprocket is behind the recoil,flywheel and stator plate. If you've gotten the cam timing off, by moving the timing chain,this is the only way for sure to get it back in time.

 

Thanks, I got it. I'll let you know tomorrow how it goes.
Dave

 

Well thanks, Old Polaris Tech, I re-did the timing from the crank to the cam, that wasn't the issue. the issue seemed to be the carb, took it out and apart. cleaned the crap out of it, I ran a stiff thread through the jets, put it back on, sprayed half a can of carb cleaner through it, and crossed my fingers. Now it runs like new. There's a little more smoke from the exhaust than before, but I think I over honed the cylinder a bit, when I replaced the piston. So I'll just keep an eye on the oil level. Thanks again for your help. I havn't riden it in over a year, forgot how fun it was.

 

Glad you found the problem. Here's a simple tool I couldn't do with out,especially on the stopped up jets that were had to blow out with compressed air even after soaking in high strength carb cleaner.Cheap and worth every penny of it's price.