Posts
540
Joined
1/29/2018
Location
Bethania, NC
US
Edited Date/Time
6/19/2018 7:33pm
This was my 2nd ride on the bike (10’ Yz250) since a complete rebuild. It did it the 1st actual ride after break in. It got hot and started doing it then. So when we got back home, I checked over the carb boots, reed cage bolts, ignition cover, etc and all were tight.
So yesterday we were riding, 10-15 minutes into the ride it started doing it AGAIN. Wtf?
FYI: We use highest rated octane pump gas mixing between 32:1-36:1. Plenty of oil.
It could be my hearing in my helmet and when the bike is doing it, it sounds almost like a “knocking” type of sound.
The bike while riding I also notice has kind of a lag to it as well. I ride woods and technical stuff so most of my riding is slow cruising/lugging through stuff and up rocks, etc. but when i open it up it “feels” like it doesnt explode like a new bike should especially for a 2 stroke.
What do I do here? Im lost as far as carb and jetting goes and depending on engine stuff...that too.
I have research the surging issue all over google through other known forums and no one seems to have the same problem as me or know of a sure answer as what it is.
So yesterday we were riding, 10-15 minutes into the ride it started doing it AGAIN. Wtf?
FYI: We use highest rated octane pump gas mixing between 32:1-36:1. Plenty of oil.
It could be my hearing in my helmet and when the bike is doing it, it sounds almost like a “knocking” type of sound.
The bike while riding I also notice has kind of a lag to it as well. I ride woods and technical stuff so most of my riding is slow cruising/lugging through stuff and up rocks, etc. but when i open it up it “feels” like it doesnt explode like a new bike should especially for a 2 stroke.
What do I do here? Im lost as far as carb and jetting goes and depending on engine stuff...that too.
I have research the surging issue all over google through other known forums and no one seems to have the same problem as me or know of a sure answer as what it is.
Grab a multimeter and test the resistence on it.
Im going through the same kind of issues on one of my bikes. It sucks.
Im not sure how coils go out. Mine went out while i was riding. They just go bad i guess.
Or you’ve got crank seal issues
The Shop
If that fixes it, you could either keep running race gas or have the head re-cut for pump.
Are you the original owner? If not, do you know for sure that the head hasn’t been cut for race gas by the previous owner?
Get a dial gauge indicator and retard the timing a degree or two. If you don’t want to do that right away, drain your gas and put in a gallon of straight race gas. If it stops, it was detonating. Seeing as it was a race bike, I’d imagine the PO ran race gas and may have had the head cut for it.
Was the dome on the head cut when you rebuilt it?
A simple thing to give the bike slightly more fuel is the airscrew, as others suggested. The other thing is to switch from 32:1 to 50:1. This will give the bike more fuel throughout the rev range, whereas the airscrew is really the first 10% of the throttle, only.
Note that 50:1 is not enough oil (in my experience) for desert racing/pro mx/running on dirt roads). If you're riding on/off throttle as you said, 50:1 will be fine for a test.
Smoke would be from oil leaking in and the surge would be from sucking a little air once warmed up and the oil is burnt off.
A lot of times you don't get a full on air leak from the primary side like you would the ignition side, since it's bathed in oil. It just gives you some strange symptoms like that, yet seems to run pretty good, overall.
Pit Row
Paw Paw
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