float height

[G11NNR]

Hi all, this is my 1st post here and hope someone can help. My son has just started racing a 2008 yz85, all was going well then the bike started flooding, changed the reed valves as they were not seating properly and as was well until yesterday. The bike started ok and away he went then the bike bogged down and wouldn't start. put new plug in ad it started 1st kick but when I opened the throttle it bogged down and wouldn't start again changed plug and same again. took the bowl of the carb and checked the jets, pilot was blocked, cleaned it and away he went again for about 30mins, he came back in and stopped for a rest then went to start bike and same problem (blocked pilot) cleaned it and away it went again. took bike home emptied tank, took tap of, cleaned filter on tap cleaned pilot and now its back blocking the jet and fouling the plug, why is the jet blocking? I read that the float height should be 19mm is that right? I have not done that yet but have to go back to it tomorrow as he is racing at the weekend and need to get it going right again. After putting new boysens in it was superb and never missed a beat. Any help much appreciated.
Gunners

 

[89blaster89]

find out what is clogging the carb, clean the carb very very very very very good, clean filter and make sure the filter boot is clean of everything

 

[G11NNR]

had carb of and used compressor to clean everything, will try a new airfilter tomorrow as well. cheers

 

[89blaster89]

try using carb cleaner also

 

[G11NNR]

ok will do just going to it now,

 

[Blaaster]

Sorry to say that if the jet is still blocking there must be still some crap in the system.

Did you remove the delivery pipe and fully clean out the entrance to the needle and seat?

Sometimes crap will lurk above the seat, and between the inlet.

 

[G11NNR]

OK folks thats me back, I emptied and filtered the fuel from the tank, took the tap of and cleaned the filters yesterday, today I stripped the carb and cleaned it then I bought carb cleaner and couldn't believe the crap that still came out, cheers for that,set float height to 19mm, fitted new fuel pipe from tank to carb and new breather pipes, cleaned the plug and fired it up and it ran fine for about 5 mins then bogged down and flooded again. I regapped the plug to 0.5mm and still no difference. I had another plug, an NGK BR8ES, and it ran absolutely perfect. I put tried the other plugs again and it was the same with all 4 plugs, NGK BR10 EIX iradium. I had a problem with the bike flooding earlier in the season and the bike was flooding and the plugs only lasted 1 race (12 mins) but that was down to the boysens I think. I know I shouldn't reuse the plugs but thought they had only done 1 race so might be ok now. I have now ordered 2 NGK BR8 EG's and 2 BR9 EG's. I trhink that when I was seeing the pilot jet blocked it was actually fuel as the hole is so small but well worth cleaning the carb anyway. My question now is what plug to run with, why was the iradium ones not lasting? I have heard about 10's being too cold thats why I'm going for 8's or 9's as he's not on the pipe the whole time.
Thanks again for the replies

 

[gb blaster]

u pre-mix your fuel right?... what do you premix it to?

Also im not sure about the float hight on a yz 85... But i was fouling plugs pretty much after every start up an i was bogged down at low rpms expecially same case my pilot was clogged(talking on my blaster)

Turns out my float hight was wrong had it to low an it was flouling bad... ill look into it an see if i can find the float hight also you have any mods for the bike an is the carb jetted properly?

 

[gb blaster]

ive looked through alot of google post an i havent really found anyhting i even found the yz 85 manual online an all it says is " carbaratours are an important part of your engine an should be sent to yamaha to be adjusted" or some horse S*hit like that but i did see a few mensions of 16 mms for your carb...

How ever if its getting to much oil i would assume your float would need to be hightened not lowered...

But in my searches i seen someone with your exact problem pretty much about the same anyways it was less detailed...

His silencer was packed with oil an the screen was completly clogged in his spark arrestor. defintally might be worth a try its easy an it fixed this guys problem right up an he was showing the same signs

 

[G11NNR]

I'm mixing at 40:1 25ml per litre, I'll take pipe of tomorrow and check the spark arrestor and see if the pipe is fouled up.
Thanks again

 

[G11NNR]

I am in the uk, is the spark arrestor for USA bikes? is it the end can? I'm a bit confused with it as all I know is the pipe has the expansion chamber and then the tail pipe.
Cheers

 

[Blaaster]

Some people fall into a trap in thinking that less oil will stop plug fouling, in most cases this is just not so.

The recommended pre mix oil/fuel ratio for an 85cc motor is around 24:1, and if the carby is jetted correctly for your elevation and temperature, you will not foul a plug!

Have you changed your pre mix ratio?

Have you cut back on the amount of oil in an effort to stop it fouling plugs.

If you have you have defeated the purpose, as the motor will run fuel rich and may not have enough combustion chamber heat to burn all the oil.

Therefore the unburnt oil will foul the plug and build carbon in the exhaust system.

Have you done a plug chop with a BR9EG to confirm that the carby is jetted correctly for your choice of oil to fuel ratio?

 

[G11NNR]

Hi again folks, I think the recomended ratio is 32:1 and I am running 40:1, I changed to an NGK BR8EG for todays race and the bike went perfect all day. All I can put it down to now was the plugs and the fact that my son is not on the pipe all the time and the engine was not hot enough and fouling the plugs, that still doesn't explain the bike starting from cold and fouling the plugs unless I got duff plugs from ebay. We are racing again tomorrow, I have put a brand new air filter in for tomorrow and that is all I have done so I guess I'll have to take it from there. Thanks for all the replies, at least now I have a spotless carb and as far as I can see a properly set up one now with all new pipes.

 

[G11NNR]

Well another successful day yesterday, 2nd overall, bike went superb no probs at all, started from cold and hot no problem. It must have been the plugs being too cold, I'll just see how it goes from here, thanks again to all the replies.