Yamaha YR plug reading

[Zonda]

Gents, as I'm a new comer to the wonders of two strokes, I need some help with tuning the carbs.

The engine has been completely rebuilt and I've fitted a Vape ignition to the bike. The carbs have been set to factory settings (balanced) and tuned as best as I can. It starts and runs well when hot, but on cruise the engine seems to miss and when I pull up at the lights it occasionally dies, on WOT it really goes hard but I can't ride it everywhere like that

So after a good 20min ride I did a plug chop and these are the results, to my (4stroke) eyes it looks to be slightly lean?

This is the first ride the bike has had with the rebuilt engine (25 miles)

Rod

[Jspooner]

I'm assuming YR5? That does not look lean at all to me. If anything a tad rich, but I would leave it alone especially on a fresh motor. For starters check to make sure your slides are in properly. The cut outs should be facing the rear of the bike.

[Zonda]

Hey thanks for the reply, I've since put in new plugs and leaned out the carb. Due to family commitments I won't be able to test ride it till Monday.

Is they any way to tell if it's using to much oil? I've set the oil pump up to factory setting and was wondering what the difference is between the 1960's oils and todays 2stroke oil, can it run with less oil?

Rod

[Jspooner]

What did you lean out? Did you verify that the slides were in correctly?

Today's oils are much better than 40 plus years ago, but I still run the stock pump settings. There are some on here that will tell you to actually increase the amount of oil, if I were you I would leave it the way you have it.

[quocle603]

That doesn't look too bad at all. Try to lean it out and get a nice chocolate color. Make a small change in the carbs (needle clip settings, upjet, downjet, air/fuel mixture screws) and plug chop. You can usually tell from your throttle response if you're 4 stroking or bogging out at certain parts of your throttle.

Tape up your throttle. With these settings: 1/4, 1/2, 3/4, WOT and determine what you need to change.

[Zonda]

Sorry guys work takes me away form my bikes far to often..

So Bike is a YR2 1968, jets are 170 main, pilot 30 and needle 5D1.

The slides are in correctly and from what I've observed can only go in one way as they have a locating pin, I wasn't aware that they could be swapped so pulled them both out and had a good look, in doing so noticed that the cut aways are 1.5's not 2.0's.

So I went back to the books and it looks like the carbs are set up as YR1 carbs with the clip at the second position not the third (YR3) as I had it initially.

So I've put the clip on the second spot and wound out the air screw another 1/4 of a turn and have also as quocle603 suggested put some tape around the throttle grip and market it. So I'm hoping to get some riding in on Thursday..watch this space 8)

[quocle603]

Try to change one variable at a time and see how that will effect the entire bike. Report back.

[teazer]

If that had been a flat out run, I would have said it was rich, but a mild run tells us little to nothing, so leave it as it is for now.

Just out of interest, what was ignition timing set to and what is stock and what plugs are they?

The reason I ask is that colder plugs will tend to look as if jets are too large and that's because they don't get hot enough to self clean. Same with ignition timing, if it's retarded, the plug will not get as hot and therefore looks rich.

To read a plug to set jetting, it must be run flat out and the plug heat range and ignition timing have to be right. Plugs that are too cold might foul from time to time, but lean jetting, hot plugs and too much ignition can melt things. For now, I'd leave it as is and run it.

[pdxjim]

Best practice with an older bike like that (especially if running stock intake and exhaust) is to just set it up as close to stock as possible.

Stock ig timing, stock jet sizes, air screws 1 3/4 out (or whatever), etc.

If it doesn't run right, something else is wrong.

Of course, make sure the emulsion tubes and all carb passages are spotlessly clean in the process.

[Zonda]

Well it's just great fun now, remembering that this is my first 2 stroke road bike and it's bog stock standard, I'm still learning the intricacies of the engines and the 50 year old suspension

So wet back country roads with livestock and blind corners makes for a restrained ride. But in all 115 miles today and I'll be out on Wednesday for another 100mile run up some roads I know very well and with no rain! Sorry for the camera angle....I've sorted that out now.

Thanks to everyone for the great help and advice 

https://youtu.be/onVaPMUlWHs

[Czakky]

Looks like fun!
Recently a YCS1 popped up for sale near me for cheap, I was quite tempted.

[Zonda]

Looks like fun!
Recently a YCS1 popped up for sale near me for cheap, I was quite tempted.

Had to look them up! A 180 twin 8), a set of flat bars, some pipes and that should be a blast to ride and sound great! What condition is it in? Unfortunately they are not at all common here and even getting second hand parts would be problematic.
Cheers
Rod