97 yzf750r, super hard to start when cold. - Yamaha Forum : Your Yamaha Motor Products Community & Resource
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Go Back   Yamaha Forum : Your Yamaha Motor Products Community & Resource > Super Sport > FZ's, FZR's, & YZF 750

FZ's, FZR's, & YZF 750 FZ-600, FZ-700, FZ-750, & YZF-750

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Old 03-06-2008, 03:31 PM   #1
carzar252
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Default 97 yzf750r, super hard to start when cold.

I just picked up this bike over the week and It takes forever to get it started. I have tryed choke no choke, part throttle no throttle. all combos i can think of and nothing. if i crank it for a good long while it will eventualy start. (have to hook up a jumper battery.) once it starts it runs like a raped ape. no stumbles, flat spots, or popping, it flat hauls the mail.

when its warm it will restart fairly easily but after sitting all night. it wont. i put plugs in it and checked the air filter.

it has a d&d pipe and silencer, and a stage 3 jet kit already when i got it. any help would be good.
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Old 03-06-2008, 03:40 PM   #2
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where are you located?
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Old 03-06-2008, 04:27 PM   #3
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My first guess would be to do a compression check on it.

How many miles are on it?
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Old 03-06-2008, 07:03 PM   #4
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i live in reno nv. the bike has 19000 on the clock. though i have a hard time believing its a compression issue due to the way it runs after it starts.....
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Old 03-06-2008, 08:22 PM   #5
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Well once the engine warms up the clearance will reduce due to the expansion of the pistons/rings.. etc.

It's a good place to start for sure as it's easy and cheap to test.

Once that is rules out I would look at the carbs.
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Old 03-06-2008, 11:51 PM   #6
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in my case, it was the carbs. the low speed adjustment screws were too rich, and the engine flooded easily when starting cold. choke made this worse. just be careful when playing with them, they have a big effect on your midrange.

i'm no carb expert though.
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Old 03-07-2008, 08:31 AM   #7
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where are these adjustment screws in relation to the inlet on the carbs.?
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Old 03-08-2008, 09:12 AM   #8
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they are on the bottom back side of the carbs, recessed. they are flathead screws and very small. be careful though, you can get your bike way out of tune in a hurry.

before making any adjustments, be sure to turn each screw all the way in and count the number of rotations until they bottom out. write these numbers down so you can return the screws to their original positions if things get out of hand.

you only need to turn them 1/8 of a turn at a time to notice a difference.
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Old 03-08-2008, 06:10 PM   #9
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do the carbs need to come off to do this?
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Old 03-09-2008, 08:56 AM   #10
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I hate to stick my neck out just to have some more knowledgeable person call me a dumbass lol so I will pose this question ... Could it need a valve adjustment causing a hard start? 19000mi seems about where it would be and I have seen the hard start related to valves in person before.
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Old 03-09-2008, 08:58 AM   #11
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nope! you DO NOT want to try and take the carbs off. you'd be opening a BIG can of worms doing that

you will have to take the tank off, but not all the way, just enough to get your hand and a small flathead screwdiver to the bottom back side of the carbs. if you still have the stock airbox, you can cock the tank up on that to give you some working room without having to disconnect the furl lines.

you mentioned that you put fresh plugs in it, did you save the old ones? they may tell you whether you are running rich or lean, that would help when you begin to play with the screws.

here's a link that has a little bit of info on what your spark plugs are telling you:

linky
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Old 03-09-2008, 09:05 AM   #12
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Quote:
Originally Posted by macattack View Post
I hate to stick my neck out just to have some more knowledgeable person call me a dumbass lol so I will pose this question ... Could it need a valve adjustment causing a hard start? 19000mi seems about where it would be and I have seen the hard start related to valves in person before.

that's a good question.

i had a few of my valves replaced at 12K miles. i had no compression on #1 and crappy compression on #2. the bike started just fine, just wouldn't run up top.

he said that his bike ran perfect up top, so i bet his valves are ok for now. your right though, i think 20K is high time to have them adjusted AND checked for compression.

these early genesis engines have a "stellite" coating on the intake valves that has a nasty habit of cracking off. that's what happened to mine.
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Old 03-09-2008, 09:53 AM   #13
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Quote:
Originally Posted by shake and bake View Post
that's a good question.

i had a few of my valves replaced at 12K miles. i had no compression on #1 and crappy compression on #2. the bike started just fine, just wouldn't run up top.

he said that his bike ran perfect up top, so i bet his valves are ok for now. your right though, i think 20K is high time to have them adjusted AND checked for compression.

these early genesis engines have a "stellite" coating on the intake valves that has a nasty habit of cracking off. that's what happened to mine.
I see what you are saying when a valve failure happens the bike wont run good on top. it seems like a lot of speculation anyway probably better to take the bike into a mechanic for some diagnosis. i've seen bikes in need of a valve adjustment sometimes wont start with out a lot of crank time but once started they still run good enough to ride maybe a little rougher than normal.
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Old 03-09-2008, 10:20 AM   #14
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thanks a bunch fellas. im gonna have my mechanic over at 2 wheel performance look at it this week. probly have the valves done just for shits and see about the tune on the carbs. the plugs were saying "too much fuel" and perhaps a little evidence of fuel additives based on the link on reading plugs.

I've been racing cars for quite a while now but i have found that its a whole new game with the bike motors.... not as easy to figure out wtf is going on.
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Old 03-09-2008, 03:59 PM   #15
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be sure to ask him to check the choke linkage. the linkage may be holding the plungers open, which would make you plugs read rich.
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Old 03-09-2008, 04:12 PM   #16
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post pics of the bike
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Old 03-09-2008, 05:21 PM   #17
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I'm new to the forum, so I'll stick my neck out there. I've owned four 750R's and put a fair amount of miles on each of them. With 19K miles I agree you should do a compression test; its easy and will rule out a great many things. I rode my first 750R over 20K and never had an issue with cold starts. My gut feeling is that your starting problem is caused by the pilot curcuit being too rich. I live in Helena, Montana @ approx 4000 ft elevation; Reno is @ 4500. I have my mixture screws set at 2.5 turns out and that may be too rich. Also, check the condition on the pilot needles themselves, someone could have seated them too hard and damaged them. Hope this helps.
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Old 03-09-2008, 06:22 PM   #18
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It's great to see so many 750 owners here... I love it!
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Old 03-09-2008, 06:38 PM   #19
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Quote:
Originally Posted by carzar252 View Post
thanks a bunch fellas. im gonna have my mechanic over at 2 wheel performance look at it this week. probly have the valves done just for shits and see about the tune on the carbs. the plugs were saying "too much fuel" and perhaps a little evidence of fuel additives based on the link on reading plugs.

I've been racing cars for quite a while now but i have found that its a whole new game with the bike motors.... not as easy to figure out wtf is going on.
I hope it is something easy to fix. I also think it would be a good idea to do what R1l said the compression thing seems logical. any of the possibles given seem logical , so its good you are taking it in- good luck.
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Old 03-14-2008, 11:47 PM   #20
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well, got the bike into the shop this week... and my guy says there are seals of some kind on the choke mechanism some where that are not allowing the choke to do its job... parts arnt available seperatly so the whole choke shaft seals and misc parts have to go in there too.... but i should have her back next week end and ill post up some pics.
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