karl thomas

hi maybe this has been awnsered before but i could not find it i have a fg stock zen 26cc was working gr8 but all of a suden its just gone waki the haskets seem fine iv pressuerised the inlet and no leaks there . the ldle is a tad iffy... it will stay rised high rpm the settle down if i pull full throttle it just lags and after maybe 30 seconds it picks up into the high rpms and i have my power back i used to be able to wheel spin off the line but now it struggle to move any one know why?

DarkFire989

Probably an Airleak. Spray WD40 in the carb, if the RPMs shoot up I believe then you have an airleak.

Foxy

Check the piston ring.

karl thomas

done both of them no luck i will start her up agin today as i have retightened evrt thing up

kingmaruirc

lag responce is a air leak. check the carb gaskets. If you see lots of air bubbles in the primer bulb the it is an air leak. The primer bulb should be filled with fuel.over 1/2 way. Or too much oil ratio.

karl thomas

nope checked that;( do i need new carb this happened before

circa5angles

could be something stuck in the carb, try blowing out the carb. I dont know?

karl thomas

damm

mooman007uk

how much slop in the throttle shaft in the carb, i just had to replace one cos it was pretty worn and gave me an erratic idle, also check the needle orings for wear/damage. it definitely sounds like an airleak, how old is the bottom end...crankseal maybe

kingmaruirc

You don't need a new carb? Try a rebuild kit. The gaskets can go bad and you won't even see it untill you take the carb apart. Usuallly the metering gasket or and the filter screen need replacing. This causes the engine to lag or bog loosing top end.[8D]

splcrazy

im having the same sort of problems on my second 5b , i suspect its an airleak from the exhaust not sealing properly to the head , and im getting black exhaust oil spraying down onto the gearbox ,[(this applies to you if its for a 5B)- also check that the throttle cable isnt rubbing under the engine shroud where the little bolt is on the right hand side bolting the shroud to the side of the head ] .
my carb is brand new 813 carb , but the piston has been through quite a few tanks now so im starting to suspect that aswell , before the build i put on a new cylinder head and new ring but the piston has not been changed , also all gaskets are brand new and sealed with sealant . so the erratic idle behaviour im suffering is pissing me off aswell . Im going to whack in a complete new ring and piston and grind the flange on the exhaust and on the cylinder head to give it some bite when i put on the new exhaust gasket with some exhaust goo .

kingmaruirc

Some people report haveing problems with the 813 carb with poor idle. The lag in responce is due to a Air leak or the engine not getting enough fuel. The exhaust port is not the problem. The problem is on the intake side of the engine. You can run a engine with no pipe or muffler. It will be real loud! So check everything o the intake side , gas tank, lines, carb, intake manifold all gasket filers. The excess oil from the exhaust manifold can be fixed by reducing the oil mix from 25: 1 to 40:1.

mooman007uk

I agree, air leaks on the intake side are the root cause of bad idle, I only run 813's and have never had an issue with idle unless I've had an air leak. The main issue I believe some have is cos they keep blipping the throttle like you can with the 668 but the 813 keeps squirting gas in the motor from the accelerator pump when you keep blipping which loads up the motor and craps out the idle. You have to use a slighly different throttle style with the 813.

splcrazy if everything else is sealed up then I'd bet on a crankseal, someone on rampage forum had the same deal and it turned out to be a seal, low compression wont give you an erratic idle but will give you lag thru the whole rev range. if the compression is real bad then it just gets real hard to start.

splcrazy

the compression is still sort of okay , the engine seals are brand new , this is running on a ts induction crankcase i have exactly the same specs engine on my first 5B and it idles and purs like a kitten , except that the exhaust on the first 5b is airtight and doesnt leak at all .

karl thomas

i just neede a full rebuild on my engine its been thrashed so much and its so old ill give it a rely good service and ley u know how it goes

splcrazy

i just rebuilt mine today and did some adjustments , im gonna give it untill this sat untill i start it up , i want the gasket sealants and threadlocker on the exhaust bolts to cure before i take it for a run