1984 Yamaha Maxim 400 wont go above 4500 rpm

so i picked up a 1984 yamaha maxim 400 and it leaked allot of oil and would rev to about 8000 then pop and sputter a bit so here is what i did

i took the hole top end of the motor off took pistons out cleaned them and put it back togather allso to note i took one piston out at a time.
put it all back togather and now it is stuck with a max rev of 4500 then sputters and pops i checked and recheck the cam timming and it looks good

the bike idles pretty good somthing to not if i drive for a few mins somtimes i loose all power/rpm (sputters and pops)

tryed cleaning the carbs 5-6 times thinking maybe i would find somthing but it allways looks clear i blew it out with compressed air check the top rubbers for the needle valve it looks good

checked both coils primary i get 3.1 ohms and secondary i get 8.0 ohms

i did a petcock rebuild all new seals lots of fuel flowing

tested batt voltage sits around 12.4-12.7 when off for a period of time

checked timing with timing light seems to be bang on at idle 1150-1250

jet sizes are 127.5 in left 120.0 in right tryed richening and leaning idle fuel screw and high speed needle no change other then the plug went from nice brown to black

if i pull one spark plug and run it off one it can do 1800-2000rpm full open tryed on both cylenders same result

checked power on the tci seemed good but i dont know allot about testing them i got 12.4v on grey/orange/red

cant think of any thing els at the moment

thanks in advance

allso i have been looking in a workshop manual online

i have been stumped on this for like 3 days

so i looked at the bike for a few more hours today and i built a home made carb sink kit

synced the carbs then took them off noticed that the right side has to be open slightly for them to be synced
Could this mean i have a sticky valve????

Just a guess or 2...

Since you have been trying to kill your TCI module (by running the bike with plug wires disconnected), maybe you succeeded. It may have been failing already. Mine had similar symptoms when it was on its way out.

That said, carbs are almost always the cause of such issues. You didn't mention if the bike is stock or modified, so I'll stop guessing there.

16VGTIDave said:

Just a guess or 2...

Since you have been trying to kill your TCI module (by running the bike with plug wires disconnected), maybe you succeeded. It may have been failing already. Mine had similar symptoms when it was on its way out.

That said, carbs are almost always the cause of such issues. You didn't mention if the bike is stock or modified, so I'll stop guessing there.

Click to expand...

bike is stock bike was acting up befor i tested each cylinder seperate
so i gues my next question is is there a way to test the tci i did test the red wire 12v i tested the 2 wires that go to the coils tested power there 12v (grey wire) (orange wire) at tci

16VGTIDave said:

Just a guess or 2...

Since you have been trying to kill your TCI module (by running the bike with plug wires disconnected), maybe you succeeded. It may have been failing already. Mine had similar symptoms when it was on its way out.

That said, carbs are almost always the cause of such issues. You didn't mention if the bike is stock or modified, so I'll stop guessing there.

Click to expand...

by the way just noticed you are not to far away im in london on

You can download a copy of the DOHC manual from one of the sticky threads here. There are detailed instructions on trouble shooting the ignition and TCI module.

Not far at all! Less than an hour by the scenic country roads!

16VGTIDave said:

You can download a copy of the DOHC manual from one of the sticky threads here. There are detailed instructions on trouble shooting the ignition and TCI module.

Not far at all! Less than an hour by the scenic country roads!

Click to expand...

one thing to note but i didnt realize that the main jet had a sleeve that could be removed so i pulled that out tonight and im hoping that after cleaning that it will be good to go. hoping all it is is a carb problem becouse kitchener motorcycle wrecker wants $110 for a tci

any ways ill be testing the bike tomorrow to see if that main jet sleeve clean did any thing ill be back with the out come tomorrow around noon

Yup, that is what the local shops want for TCI modules around here. You might also want to check with NCK Cycle ( http://nckcycle.com 519-533-5177) in Woodstock. They had a TCI from a Seca (a few years ago) for $100. Same part.

lol just my luck i get the carbs all togather and back in the bike i go to start the bike and the battery is dead then realize last night when i put the steering lock on it switched to park so the rear running light was on all night so ill fire it up in about an hour or so let the battery charge a bit and with any luck

16VGTIDave said:

Yup, that is what the local shops want for TCI modules around here. You might also want to check with NCK Cycle ( http://nckcycle.com 519-533-5177) in Woodstock. They had a TCI from a Seca (a few years ago) for $100. Same part.

Click to expand...

so i think i may have narrowed it down it seems like the right side is the one that is popping and sputtering so in a little bit im gonna try changing the coils around
allso today i pulled apart carbs again they looked clean but i said screw it and boiled them for 15 mins on the stove in water with simple green water looked good so i poked and prodded with guitar string came out clean im hoping with any luck it is a coil going bad and ill check out that nck thanks

so im back to being lost was wonder if any one can pipe up with a voltage test on there tci box

not running





and this is with it running the same wires




and here is the battery well engine is off


if some one can just test theres to see if voltage drops on the orange wire and then test the grey wire

by the way the key was on for for the tests on tci box

allso do the orange wire as well the is beside the grey on the 4 pin connector

so im trying to get a new/used tci in hopes that that will fix my issues

SUCCESS so after a week of trying to figure it out dave was correct tci was faulty got a new one today and bike runs like a scarred rabbit thanks dave