yz426f 400ex hybrid issues

[TRXordie]

anybody out there having overheating issues. running a 250r rad
and multiple heat sinks. also very difficult to start hot. any suggestions?

[ZRider400]

stock 250r radiator probably wont cut the mustard.

I would go with a PWR, check ebay for deals, i picked one up on here for 150 bucks not long ago.

Put a over flow bottle on it to catch anything, along with a hi-pressure rad. cap.

If it starts hard, check your valves, probably out of adjustment.


also.. run engine ice :D

[TRXordie]

thanks ill give it a try. im new to to the yamaha world and appreciate the help.

[ss440ex]

I`ve ran a 250r radiator on my yz426...with no problems.

Along with 4 others I ride with...Texas heat also.

Is the water pump impleller in good shape?

Good luck.

[TRXordie]

im going to check the valves in the next couple a days. while i've got it in the garage ill check the pump too. i have engine ice in it right now as well as an overflow bottle. i have a temp gauge on the rad inlet hose. spikes over 250 degrees and pukes out coolant if you arent moving fast. thanks for all the suggestions.

[yamahopper]

i'm having the same issues except my valves are in spec and i don't have an overflow bottle just some tubes running out below the frame. I am running an oversize radiator though...i'm stumped.

[kyledvor61]

same as well.

[hontrx265r]

check your head gaskets fella's.. Use oem if possible, and use correct torque sequence. common problem on the yami's

[TRXordie]

i took the valve cover off and checked the timing and the valves. timing is right on. the valves are less than .002" tighter than the should be on intake and exhaust. im assuming that isnt bad enough to cause a hard start issue...? let me know what you think

[ss440ex]

Are you using the HOT start on the carb, when you are trying to restart.

Give it NO gas when kicking.

Good luck.

Also are you using an auto decompression exhaust cam?

[yamahopper]

Originally posted by ss440ex
Are you using the HOT start on the carb, when you are trying to restart.

Give it NO gas when kicking.

Good luck.

Also are you using an auto decompression exhaust cam?

no i'm not using the hot start on the carb... the red nob right? or is it the black one? and no i have the stock cams in mine ( using the decomp lever still)

[usp4u]

hot start is the red plunger. defintaly use it. dont give it any throttle at start up. black knob is idle speed adjustment.

[ss440ex]

Look like this....

[yamahopper]

yep and i'm guessing the other black choke nob is for cold start choke? i'm new to the dirt bike carbs.

[usp4u]

correct.
blk plunger-choke
red plunger-hot start
blk knob-idle speed