Underpowered and terrable fuel economy

I only just bought my bike yesterday (A Yamaha 750 Maxim) and i think the guy may have taken me for a run around.

So i figured out yesterday that the bike seemed underpowered. but i have nothing really to compare it to except a honda 350 duel purpose bike. and i think it had more power but i didnt get much time to ride it.

Today i decided to take the bike for a drive to the next town over. a 1 hour ride and once i got it on the highway another bike passed me when i was pullin it as hard as i could. like 7000 rpm full throttle in 2nd gear. and as i went i couldnt even catch up to him or anything if i tried. he wasnt speeding or nothing but my bike is having a real hard time doing 90 km/hr

anybody have any ideas on this?




when i got home i pulled the air filter out and when it was running i noticied that the crank case breather is pushin quite a bit of smoke.

id really like to drive the bike south for the summer so any help is very greatly appreciated.

Taylor.

 

smoke from crank case breather is sign of worn piston rings. that smoke is called engine blow by.

do a compression check.

i had a hard time on mine getting up to 75 mph. no mufflers fixed that problem.

 

2nd the compression check. Pull the plugs and put up pictures so we can see.

MN

 

I quickly googled on how to restore engine compression.. i found a goop iv used before and put a bit in.. Engine Restorer i think its called.. .didnt work...

Reading your comment.. i pulled the plugs and took pictures of them..

1 and 2 are dry and rust coloured.. 3 and 4 are a bit wet.. the engine was still hot when i pulled them.

 

never use that engine restore crap. your just wasting your money. if the motor is bad the motor is bad and no chemical restore is going to help.

plugs 3 and 4 aren't firing. that's why they are wet. you need to find out why. either you've got no spark for some reason or those carbs are sending too much gas into the cylinders.

put those plugs back in the caps and lay the plugs on the engine and crank er over. see if there's spark. if not. try the dry plugs in those caps and see if THEY spark.

you need to figure out if the plugs are bad or if the wires OR caps are bad in the coils.

 

IMHO, you might as well just get new plugs and plug caps. $30 and you probably need them anyway.

Look through HEREto see how to check your coils. However, a bad coil would not cause 3 and 4 to not fire. (1, 4 or 2, 3)

+10 on compression check and spark check.

That link s Chacals catalog, pg 2. You might find a lot of what he has to say there very enlightening.

 

Its too late to get new plugs and caps.. nothings open any more.. but i will surely try and see if i have spark on those two cylinders.

you guys are awesome i really appreciate all the help you've given me.

 

so i pulled plugs out of an old suzuki samurai that were clean enough.. i checked them on the bike for spark.. worked good checked my two clean plugs from the bike.. working good..
put them in and fired the bike up.. it started and idled normal.. then reved up to around 3000 rpm.. thats not unusual. warm up sequence i believe.
then i put my gear on and turned the bike around and it started idling at 5000 rpm.. oh well it sounded better than it did before.. pulled out onto the road.. hmm that was easier than usual.. bliped the throttle and slid back on the seat.. that thing is something else.. fixed the problem by adding the 2 other cylinders and holy smokes thats got some power..

so since im new to street bikes.. i now understand why you guys do what you do...

in driving around i friggin love that bikers wave to one another.

but my new question is what would cause it to idle so high?

i drove it around a 10 km loop and found it to be great at accellerating.. but since its trying to idle at 6000 rpm its kinda hard to slow down.

iv got a theory that the guy before me tuned something up so it would run nice so he could sell it.

any new ideas?

thank you again you guys are amazing

 

Your carb slides may be sticking. You'll need to make sure you have some slack in the throttle cable.
If the cable has slack you'll need to pull the carbs and give them a good once over.

MN

 

it wasn't running nice. it was only running on two cy linders. therefore, the idle was set for those two cylinders.

now that you've got all 4 cylinders running. y our going to have to bring the idle back down by adjusting the idle screw. underneath the backside of the carbs between 2 and 3 should be a fairly good sized handle to adjust. you can reach in there and turn it with your own hand.

adjust your idle to around 1000 or slightly above.

then get 4 new plugs as your suzuki probably runs a different number. which means a different heat range in the spark.

 

When you adjust your idle, make sure you adjust it on a well warmed up engine. Trust me, if you don't you will be fiddling with it forever.

The 86-95 Suzuki samurai plugs are BPR5ES. Dont use those anymore!!!!!! They are too hot and will cause detonation, expecially in an cylinder that has lots of carbon deposits from misfires.

Oh, and do what rick says to do. In your signature, put your year and model of bike. Also, ensure your location is stated under your profile picture. You can do these all from your Account page.

This won't be the last time you need us.

 

i tried to lower the RMP's with the throttle stopper that's just behind the carbs but theres a point where it stops lowering anything. iv got it kinda sitting around 2200 rpm idle.. its allot better. 6000 was just plain dangerous.

 

I had a similar situation. The sync was so messed up it was doing the same thing. I would still pull the carbs and follow Rick's old school carb cleaning. Once you bench sync you'll be pretty close and the bike should idle alot closer to the 1000 rpm that it should.
Also I second , get the right plugs.

MN

 

Loosen up the adjusting nut on the throttle cable at the handlebar too.

Once you change the plugs and caps, ride it for awhile to clean out the nonfiring cylinders. Gently at first, then progressively harder to burn off the carbon. We can start troubleshooting from there. You can't do so much as a compression check where you are at now.

Also, you should be able to see the idle screw touch the throttle plate. Screw/unscrew it until it is just touching. I assume if it really isn't doing any good they aren't touching anymore.

 

Thanks MN....don't do anything till you get the right plugs! I had those same plugs in when I got my bike, and it barely ran. New ones and I was riding to work everyday.

You risk serious damage to your pistons if you keep running the bike and adjusting things.

Sit back and relax until a store is open...I know it's hard. But it's in your best interest.

 

go to the auto parts store. they sell ngk's. get all 4 plugs and go find that 350 you said was kicking your butt.

i bet you'll KICK HIS butt now. now that you've got 4 cylinders running instead of 2.

 

So my 750 is fixed up and running better.. I still havnt adjusted the idle so it sits properly.. i backed it off too far and havnt taken the time to put it back... it idles at 900 rpm.. and somtimes it stalls.. so i just play and rev it up a bit when im stopped. sometimes when i stop riding and go to park it likes to push its revs up to 3000 and im not sure why at all.. i dont know if its just fuel bumping around in the carbs when i put my centerstand down or what but its annoying. and before i put proper spark plugs into it i think i had more power than i do now.. either that or im getting used to the bike too quickly.. i drove my truck yesterday and it felt so lumbersome. its the fastest 4 wheeled machine iv ever owned and its so lame now.. this bike is such fun..

i was wondering what do you guys do about the brutal winds when you hit highway speeds?

and sombody here said switch the plugs and caps.. are the caps the plug wires or what? cause i didnt change em.

 

Winds? You'll get used to them. Scared me shirtless at first. Some people have a windshield. Probably a good investment for a commuter like me....

The plug wires are not like you're used to. They are inseparable from the ignition coil. The caps, however, screw off the wire. The cap contains literally a screw that screws into the wire. You should check the resistances on your coils first, if they are bad you will replace them with a different style, from what I understand. I'm pretty sure I posted the link above.

Do make sure your idle is correct, it will keep it from stalling, even though it sounds like you have some other problems going on. My first guess about the rev while parking would be the throttle cable pulling when you park, but without knowing your exact sequence it's hard to say for sure.

My bike stalls out due to a lean condition too when the idle mixture screws are 2.5 turns out. You might (if fact it's very very likely) need to clean your carbs.

 

get the carbs adjusted and synced. out of sync carbs always cause various idles and different temps.

i don't think i'd worry about the plug caps. just change the spark plugs. the main thing is to get the bike running so you can drive. and adjusted properly. everything else you can do WHILE your enjoying the riding.

and 4 cylinders is always more powerful then 2 cylinders.

 

Oh, first things first!!! Don't Die!
I only say caps b/c for the $15 and 30 min, it was a huge improvement in the performance of my bike. I wish I had done it when I got new plugs the first time around.

Don't forget that before you sync, you need to do a valve adjustment.

In fact, you probably need to do every maintenance item in the book. I know I did. Plug caps and idle mixture setting aren't in the scheduled maintenance, at least not in the Haynes manual. That doesn't mean you shouldn't do them, of course.

 

where can i find how to sync my carbs and adjust the valves? do i have to pull them?