Yamaha Jog - cutting out and sluggish acceleration

[terwiliger]

I bought a 98 Yamaha Jog three months ago and was very pleased with how zippy it was.
But over the last month there has been a noticable difference in the time it takes to accelerate - partiularly after I've started it from cold.
Once I get going on a straight stretch of road it's alright...but if I have to stop or brake for any reason it really struggles to get up speed up again.
My speed also fluctuates wildly...I'll be travelling along full throttle at 50 km/h and will feel the engine jerking around and suddenly it has dipped down to 40 km/hr and then it is off again and my head is whipped back.The first 5 minutes after starting it up are the worst...the engine keeps cutting out and every so often will virtually die - coughing away and barely moving.

Please help me! It gets quite scary on Dominion road when I can't trust my scooter to perform. Also please excuse my untechnical language.

[mainepeace]

Check the carburetor. There may be a clog. I believe it has a slide type carb (I'm working on a 04 Jog at the moment). My guess is the float is sticking or the float valve is clogged.

Also check the spark plug and the spark plug boot for a loose connection. Check the air filter too, but I bet that it's a fuel issue.

Greg

[skuttadawg]

Yes the air filter gets dirty and can be cleaned , fuel filter can be changed and the jets can be cleaned . Remove the carb and its bowl on the bottom to access the jets that screw out to clean with any carb cleaner spray .

You really need to let it warm up some BEFORE riding it as it will run better and last longer

I think its a 2T as my friend Jog was 2T they run best of premium synthetic 2T oil like Bel Ray or Royal Purple and never use the weedeater junk as it will smoke more , foul the plug easier and not perform as good .
2Ts burn oil and gas so its common that plug will get dirty and need to be cleaned and a good idea to check the gap while you have it out . The NGK irdium spark plug fires much better and less likely to foul out from oil build up than the others .

How many miles are on it ? Rings wear out and can be replaced for cheap and restore compression which will improve performance . On the top off the carb the needle diaphragm can develop a tear and mess up how it runs . Also the needle that goes through it should have a clip to be able to change the needle position if needed .

Drive belts wear out and stretch before breaking . A stretched out belt will not perform as good as one that is snug . These wear out and will need replacing on all scooters . A good idea is to get a Gates Powerlink as they are better than most eshop.mainelyscooters.com/product/cat-139qmb/gates-powerlink-premium-cvt-belt/ Greg can help you get the correct size if your unsure . The round roller weights will get flat spots as they wear and limit their ability to roll in the variator . Weights are cheap and lighter ones may help you go faster on take off and uphill . Slider weights like Drr Pulley brand will work better and last much longer . A performance variator will also give more top end and mid range speed . Mufflers can get clogged and may need to be repacked .

If yours is a 2T Minarelli like I think it is than this kit will really turn it into a beast eshop.mainelyscooters.com/product/cat-1p40qmb/hoca-minarelli-2t-power-pack/

Yamaha is a great brand . All scooters will need to be serviced like clean the carb etc to keep them running at their best and only need servicing instead of repairs like those that get neglected will .

Get a new spark plug with a NGK iridium or at least the standard NGK , install it and go for a WOT run and remove the plug to do a plug chop to see how the jetting is . Here is a chart to compare yours with www.4secondsflat.com/plug_chart.html A size or 2 larger main jet will help the top end speed but too large will be too rich and not run as good as a jet that matches your scooters status , like the flow rate and condition of the engine . If you ever have any idle issues even after cleaning the idle jet sometimes a size up idle jets fixes it . The small jets are easy to clog and will need to be cleaned as needed .

I have this compression gauge as it is handy to know the PSI in the cylinder for reference and troubleshooting . It is only 20 dollars and can be real handy www.harborfreight.com/compression-test-kit-66216.html