Problems with jetting/mixture?

[fd235158]

Hi everyone,
I just finished a project 86' Suzuki lt250r quadracer. I know it's not a dirtbike but the engine seems pretty similar to my 02 RM so I'm hoping some of you can help me. Now for the story: I bought a junked quadracer and have completely restored it. All new bearing, seals, gaskets, carb kit, wisco top end kit bored .080 over, etc... While I was testing everything I put a cap of Belray H1R 2 stroke oil in the spark plug hole just to lubricate when turning the engine over. After a lot of starting fluid I got it running, but it wouldn't idle. I'm running a 30:1 mixture right now (manual calls for 20:1 but thats almost 20yrs old and not based on synthetic oil) and have all the jets standard, needle is in the 3rd clip, air screw is 1.5 turns out. The day after I initially got it running it wouldn't start. I replaced the plug and still nothing. Finally I pulled the thing behind my truck because my leg was going to fall off and I got it pop started. After about 5 minutes of running the new plug puked on me. I replaced it and it started after 2-3 kicks but still wouldn't idle. I tried to start it today and nothing except the smell of a flooded engine after 2 dozen kicks. Any advise on what might be the problem would be very appreciated. I'm thinking I need to either lean out the premix or adjust the jets. I just don't know what jets to adjust because it runs fine in the mid range. Thank you for any help you give.

 

[reelrazor]

I wouldn't start playing with jets just yet. If yo really think it is carburetion, I would go back into the carb to make SURE everything is right(note: especially airbleeds and float needle).

I am assuming that since oil was used during assembly of the bottom end(very likely), the rings were likely smeared with oil(at least) and your "capful" of oil in the plug hole plus your 30:1 mix, that you have a puddle of oil in the crankcase. The starting fluid didn't help any as it washed any oil up top down past the rings. You end up with atomized 30:1 picking up more oil(not atomized) and spitting it up the transfers and onto the spark plug(which fouls). Midrange may be where the crankcase pulses leave the puddle alone or the pumping action isn't quite in harmony to throw it up top.

You didn't say how long you ran it the day you got it running. I am also gonna go out on a limb and say it was prolly smoking pretty good and you didn't run it that long.

It is quite common for rebuilds to puke a plug or two the first couple runs. I always like to run 'em long enough to get fully hot the first time starting. Once you have done that a couple times and let it cool down, you can wring it some to clear up that excess. Initial run/break-in is about the ONLY time I will beadblast and swap plugs out. I do very 'dry' rebuilds/break-ins myself(years of dealership wrenching-my own shop). It's a two stroke-as soon as the engine pumps, it is getting lube.

Ohh, more on starting fluid; if you need to spray something to encourage a two stroke to start, use WD40. Ether(starting fluid) washes oil film away(thins it). WD is at least a minor lubricant.

 

[fd235158]

Sounds like I shouldn't play with the carburator until taking it to the trails for a day. I was only running it for 10-15 minutes the other day, so I'll see if it improves after a full day. Thank you

 

[fd235158]

Reelrazor, I went for a little ride today and the longer I was on it the better it got. After about 20-30 minutes it even started to idle a bit. I was wondering if it would be wise to run the fuel to air mixture a little lean. Thank you so much for your help

 

[reelrazor]

Set the mix screw when it is fully hot. Start around 1.5 turns out. Have it running, but keep a hand on the throttle so you can blip it if it tries to stall. Turn the screw in sloooowly, counting turns(or fractions of). It will either want to idle better, or get worse. If it gets worse, turn it back to 1.5 and go out slowly, listening for a better idle. The idea is to find at what point the idle gets worse in each direction(lean and rich) and set it for the midpoint. Example; if you start at 1.5 turns out, and it won't hold an idle at 2.25 turns out, and won't at 1.25 turns out, then set it at 1.75.

Rule for idle mix screws; if the screw is downstream of the slide, more turns out = richer. if the mix screw is upstream of the slide, more turns out =leaner

 

[matt-itude]

I helped a kid with a similar problem on a quad racer and his prob was a sheered key way on the fly wheel. we tried a few jets first though. it was a hair puller to figure.