XS750 Starting problem - Help Pleeaassee

Angelo

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Mar 11, 2004, 6:46:22 AM3/11/04

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Hi, my XS750 triple does not start after a top end job. I'll
appreciate any advise as I am at my "wits" end.
Done so far:-
1) Bored out cylinders and replaced pistons and rings with 1st
oversize.
2) Replaced base, cylinder head and tappet cover gaskets with new.
3) Set cams and timing disk to marks and 1F TDC respectively.
4) Checked "free" rotation by turning crank with a spanner.
5) Oil and then attempt to start.

After many attempts with no luck just the odd backfire, checked
compression which was totally lacking in nos. 2 and 3, and low in 1.
On suggestion of mechanic friend that I may have set timing out by 180
degrees, reset timing accordingly.
Still no luck but more frequent backfiring, now compression is totally
lacking in nos.1 and 2 and hign in 3 !!!

I do not believe that I have damaged the valves as I have always
checked that the crank rotates freely by hand.

Any suggestion on how to troubleshoot further, and how to make sure
that TDC is on the power stroke as the Haynes manual does not have
this detail?

BTW. I have an electronic ignition.

Angelo
1979 Yamaha XS750

David Ward

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Mar 11, 2004, 7:54:52 AM3/11/04

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"Angelo" <ang...@absa.co.za> wrote in message news:f0f70e0a.04031...@posting.google.com...
: Hi, my XS750 triple does not start after a top end job. I'll

: appreciate any advise as I am at my "wits" end.
: Done so far:-
: 1) Bored out cylinders and replaced pistons and rings with 1st
: oversize.
: 2) Replaced base, cylinder head and tappet cover gaskets with new.
: 3) Set cams and timing disk to marks and 1F TDC respectively.
: 4) Checked "free" rotation by turning crank with a spanner.
: 5) Oil and then attempt to start.
:
: After many attempts with no luck just the odd backfire, checked
: compression which was totally lacking in nos. 2 and 3, and low in 1.
: On suggestion of mechanic friend that I may have set timing out by 180
: degrees, reset timing accordingly.
: Still no luck but more frequent backfiring, now compression is totally
: lacking in nos.1 and 2 and hign in 3 !!!

I've seen this mistake before - valve timing can't be off 180 degrees
from the timing marks, but rather 240, since it's a triple.
Reset the cams to the service manual indicated markings while
noting the position of the pistons. Do the free rotation again
and watch the piston position for all three and see if, in fact,
that the valves are closed at TDC for each jug in turn. Make
sure you spin the engine the correct way, and make sure
you haven't mixed front and back cams.

Best. One of my all time favorites was the '79 XS 750.
I dustbin fairing'd mine, and had Kerker custom build
a 3-into-4-into-2-into-1 exhaust for a Rajay turbocharger
setup. Would handily redline in high gear on the quarter
mile, and never broke.

Dave

Angelo

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Mar 12, 2004, 8:25:37 AM3/12/04

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"David Ward" <dsw...@earthlink.net> wrote in message news:<wkZ3c.14689$%06....@newsread2.news.pas.earthlink.net>...

Thanks Dave, you've made me realise that the timing chain cannot be
set wrong if I'm pointing everything to the correct markers.
Can anybody please explain how to check the ignition timing?
Could I be at TDC but "igniting" on the exhaust stroke?
How do I check which cylinder is firing when? I know a little about
ignition systems and even less about electronic ignition :(
also
What checks can I do to the head and valves without removal? (if any)?

Tks. again in advance
Angelo
1979 XS750 "Not going anywhere yet :( "

Kim Neubert

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Mar 12, 2004, 2:34:03 PM3/12/04

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You said you have no compression in a couple of cylinders. That' NOT
ignition timing it's cam timing.

Noob

Charlie Gary

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Mar 12, 2004, 7:01:50 PM3/12/04

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"Angelo" <ang...@absa.co.za> wrote in message
news:f0f70e0a.04031...@posting.google.com...

><<Snip>>
>
> Angelo
> 1979 Yamaha XS750
>

I couldn't find the part where you mention checking valve lash clearance.

--
Later,

Charlie

Fix the e-mail address and it will get to me

Fitchin

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Mar 12, 2004, 7:38:38 PM3/12/04

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Give that a try (checking valve clearance). I had one heck of a time getting
my Kawasaki 454 LTD to start. Someone mentioned to me to check valve
clearance. Adjusted the valves to proper clearance and she fired right up.
The intake valves were out slightly. Funny enough, it was only really
difficult to start when outside temp was cold.

Good luck,

Craig

"Charlie Gary" <cg...@modelnospamtodaywerks.com> wrote in message
news:Obs4c.58042$E76....@newssvr33.news.prodigy.com...

David Ward

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Mar 12, 2004, 11:12:34 PM3/12/04

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"Kim Neubert" <no...@raex.com> wrote
:
: > Could I be at TDC but "igniting" on the exhaust stroke?

: > How do I check which cylinder is firing when? I know a little about
: > ignition systems and even less about electronic ignition :(
: > also
: > What checks can I do to the head and valves without removal? (if any)?
: >
: > Tks. again in advance
: > Angelo
: > 1979 XS750 "Not going anywhere yet :( "
:
: You said you have no compression in a couple of cylinders. That' NOT
: ignition timing it's cam timing.
:
: Noob

:
:
Sounds true. It's gotta be mechanical. I wouldn't mess w/ the electrics
till the mechanics are squared away.
As far as the head and valves are concerned, take the top covers back
off and manually turn the engine while monitoring piston movement.
Actually watch the entire sequence of valve train movement through
720 degrees and see that it makes sense. Do a leak-down test at
each tdc as a final check. Once you're absolutely certain that
everything's in order, get back to tdc on cyl 1 and do a static
timing check per the service manual. It'll have to start after
that.

Best
Dave

Pobirsm

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Mar 14, 2004, 3:16:50 AM3/14/04

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My first guess is that your valves are to tight

Bantam

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Mar 14, 2004, 9:27:14 AM3/14/04

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In article <20040314031650...@mb-m25.news.cs.com>, Pobirsm
<pob...@cs.com> wrote . . .

>My first guess is that your valves are to tight

Yes I would agree, from what I've read in the thread so far, you need to
check the clearances are correct first and then double check everything
else.
I recall somewhere reading of the need to set the timing one tooth out
when assembling. Presumably so that it all pulls back in line when you
bolt the cams down.
You may want to check for such peculiarities on the triple owners site
http://www.yamaha-triples.org/ (I've had a quick look but nothing
specific on there so it may be worth while asking on their news group)
A good few people own triples in the states and their news group is a
good source of info. as well (you can get details on it from the web
site).
--
Bantam
GSX1100F, FZR1000ExUp, XS750SE
I'd rather be riding the bike right now

Angelo

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Mar 15, 2004, 4:44:24 AM3/15/04

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Thanks to ALL!! who have responded with advise and tips.
There seems to be common agreement that valve setting is the cause.
A bit of history (not an excuse), is that I bought the bike from a
friend with a known cylinder oil leak problem(the bike not the
friend).
I believe I have fixed the oil leak (bore, pistons,rings) but I did
not do anything to the head as I know it was done very "recently".
I will be checking the settings ASAP.

Once I have the compression problem sorted, I still need to know how
to get TDC for cylinder 1 on the ignition stroke. This is not
specifically explained in my HAYNES manual and nobody has responded to
this question yet.
The manual says to set to the T mark to the right of the F1 mark. Ok,
but how do I know when its on the ignition stroke and when on the
exhaust stroke?
(BTW. I have an electronic ignition)

If this is a stupid question, let me know. (gently please).

Thanks Angelo
1979 XS750E not going anywhere :(

Bantam <Ban...@somewhere.outhere.com> wrote in message news:<Gdgl7XBC...@prettystupid.comma>...

Mark Olson

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Mar 15, 2004, 5:40:14 AM3/15/04

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Angelo wrote:

> I believe I have fixed the oil leak (bore, pistons,rings) but I did
> not do anything to the head as I know it was done very "recently".
> I will be checking the settings ASAP.

Bzzzt! Famous last words- "It can't be X, that was just gone over
by someone I trust..."

> Once I have the compression problem sorted, I still need to know how
> to get TDC for cylinder 1 on the ignition stroke. This is not
> specifically explained in my HAYNES manual and nobody has responded to
> this question yet.
> The manual says to set to the T mark to the right of the F1 mark. Ok,
> but how do I know when its on the ignition stroke and when on the
> exhaust stroke?
> (BTW. I have an electronic ignition)
>
> If this is a stupid question, let me know. (gently please).

Well, it's only a stupid question if someone's already explained it
to you and you said you understood but you really didn't.

I am not familiar with this engine but I will assume it is like most
bike engines of the era, so forgive me if I am wrong.

There is no difference between the ignition/compression stroke and
the exhaust stroke *to the bottom end of the engine, including the
ignition system*. What determines which stroke it is, is the relative
phase between the crank and the cams, which is up to you to set
properly. The ignition system fires on both the exhaust and the
ignition/compression strokes. This is why no one has been able to
tell you how to set the crank on the ignition stroke rather than the
exhaust stroke, because there is no difference, as far as the ignition
system is concerned.

--
'01 SV650S '81 CM400T '99 EX250-F13

David Ward

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Mar 15, 2004, 11:29:47 AM3/15/04

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"Angelo" <ang...@absa.co.za> wrote
:
: Once I have the compression problem sorted, I still need to know how

: to get TDC for cylinder 1 on the ignition stroke. This is not
: specifically explained in my HAYNES manual and nobody has responded to
: this question yet.
: The manual says to set to the T mark to the right of the F1 mark. Ok,
: but how do I know when its on the ignition stroke and when on the
: exhaust stroke?

stick your finger into the #1 sparkler hole. Rotate the engine until air
pressure starts to blow past your finger - which will be during the
compression stroke. Continue rotating the engine slowly until
the pressure becomes suction - you've just passed top dead center.
Look into the hole and back the engine up until you see the piston's
at TDC. Insert the timing/piston position tool and back the crank
to whatever the BTDC timing spot is, and set the ignition.

Best
Dave

Hank

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Mar 15, 2004, 1:33:32 PM3/15/04

to

Although you can get super persnickety with this(dial indicator), I just
stick a screwdriver (don't leave it there!) in the plug hole perpendicular
to the piston top while I turn the flywheel back and forth *slightly* by
hand near the "t" mark. If the rockers are loose on that cylinder you are at
tdc compression stroke on that cylinder. If one valve is loose and one is
tight turn over one full turn to get comp stroke. If both valves still
aren't loose now, you need to set valves!
btw regardless of whether the head was "done" recently you will have to set
the valves if you have the cams out.
HTH

"David Ward" <dsw...@earthlink.net> wrote in message

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Angelo

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Mar 23, 2004, 1:53:47 AM3/23/04

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Thank you to all who responded, yes the valve settings were completely
out.
In fact the head I used was the wrong one, and not the one which had
been worked on by the previous owner! (I have bought 3 XS750's - 2
with papers and 1 for spares)

The bike goes well in spite of the problem mentioned below, and I'm
going to start with the paint and other cosmetics very soon. As soon
as I've sorted out the "oil problem".
The exhaust is smoking badly and inpection of the 3rd cylinder spark
plug shows it quite wet.
I expect a valve problem.
Any suggested troubleshooting method before I start stripping the
head?
I'm down to my last 2 master links. :(
As I mentioned initially, Cylders have been bored to 1st oversize, new
pistons and rings fitted, and valves have been set.
I do not know condition of valve guides seals.
Waiting again in anticip....................pation.

Angelo
1979 XS750

"Hank" <ur...@nbnet.nb.ca> wrote in message news:<0Gm5c.117469$IF6.3...@ursa-nb00s0.nbnet.nb.ca>...

Angelo

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Mar 29, 2004, 6:10:25 AM3/29/04

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ang...@absa.co.za (Angelo) wrote in message news:<f0f70e0a.0403...@posting.google.com>...

Once again, thanks to all.
I've posted a new request for help with the smoke problem.
I just wanted to thank all and especially Mike who resolved what was
really baffling me.
How to set the ignition timing. Its so simple. The plugs fire @ both
intake and exhaust TDC. Thank you Mike!!

Angelo

miser9

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Mar 27, 2005, 8:39:45 PM3/27/05

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hi i have a xs750 i can not get it to start its ben siting for some time i
cleaned the carb and changed the spark plugs please help

The Older Gentleman

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Mar 28, 2005, 2:20:53 AM3/28/05

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miser9 <mis...@aol.com> wrote:

> hi i have a xs750 i can not get it to start its ben siting for some time i
> cleaned the carb and changed the spark plugs please help

Try cleaning the other two carbs?

--
Trophy 1200 (Doctored)750SS CB750F2 CB400F CD200 ST70 DT50MX
GAGARPHOF#30 GHPOTHUF#1 BOTAFOT#60 ANORAK#06 YTC#3
BOF#30 WUSS#5 The bells, the bells.....

biker trash

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Mar 28, 2005, 5:55:45 PM3/28/05

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It may sound stupid, but check to see if the petcock is flowing fuel
correctly. Yammi's work on a vacuum feed, so all the hosed need to be hooked
up right. If I remember right, the XS 750 has 3 lines coming off the
petcock.
You say you cleaned the carbs, but what did they look like inside? If the
bike has set awhile, you might need to get them "boiled out", and check all
the little tiny jets inside, and the needle and seats. The float settings on
Yamaha carbs is very critical.
Finally, check to make sure you have a good strong spark. On Yammi's, if
any part of the ignition is week, you will have less spark
I used to have one of those, and one day it wouldn't start. I checked the
fuel, the spark, and all kinds of things. The bike wouldn't fire until I
put a new starter solenoid on it, then it came to life.
Also, my Son has an XS 400 that will not start with the elec. starter,
Period. But 3 or 4 kicks and it will always start.

"miser9" <mis...@aol.com> wrote in message
news:ed275bc18fc480fa...@localhost.talkaboutmotorcycles.com...

The Older Gentleman

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Mar 29, 2005, 1:24:11 AM3/29/05

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biker trash <goldw...@chartermi.net> wrote:

> Also, my Son has an XS 400 that will not start with the elec. starter,
> Period. But 3 or 4 kicks and it will always start.

The XS400 twin was notorious for this (I've had a couple).

Jeff Bertrand

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Apr 1, 2005, 2:22:56 AM4/1/05

to

Make sure the petcock is in the "prime" position and that the battery is
really good. The XS750 can be a bear to start if the battery isn't perfect.
The battery for this bike has very little reserve capacity and if you run it
down even a little bit trying to crank a cold motor you may never get the
bike started If mine sat for more than a day or two, I would always kick
start it initially. Also once the choke is set DO NOT touch the throttle
when trying to start!
--
-WJB

"miser9" <mis...@aol.com> wrote in message
news:ed275bc18fc480fa...@localhost.talkaboutmotorcycles.com...

snber...@gmail.com

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Jun 9, 2020, 6:13:24 PM6/9/20

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My bike exactly, but it will start up on the first try every 2 weeks, runs great, shut it off and it wont start for another 2 weeks, cranks and cranks. Has a new rectifier and still the same

The Older Gentleman

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Jun 11, 2020, 2:12:39 AM6/11/20

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<snber...@gmail.com> wrote:

> My bike exactly,

Have you noticed you're replying to a 16 year-old post, numbnuts? OP
could be dead by now.

--
BMW K1600GTL; Kawasaki Ninja H2, Yamaha 660 Ténéré;
Guzzi Le Mans Mk.2; Honda CD200, CB400F, Yamaha 125 NMax
More secure garages needed....
neil underscore murray at fastmail dot fm

Futility Man

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Jun 11, 2020, 7:48:13 AM6/11/20

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On Thu, 11 Jun 2020 07:12:37 +0100, totallyde...@yahoo.co.uk (The Older
Gentleman) wrote:

><snber...@gmail.com> wrote:
>
>> My bike exactly,
>
>Have you noticed you're replying to a 16 year-old post, numbnuts? OP
>could be dead by now.

And I bet the damn thing still won't start.

--
Futility Man

The Older Gentleman

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Jun 11, 2020, 2:02:03 PM6/11/20

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Genuine chuckle here.

Larry Reimer

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Aug 2, 2022, 12:47:57 AM8/2/22

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To; Angelo ..I bought 1978 XS750f triple from a friend that had not run since 1986 .. I freed up the engine , I did get to run ...The XS750's have a problem with the starter drawing more amps from the battery that the battery can handle leaving only 3 volts at the coil when running the starter , the coils require atleast 6 volts to work ...I removed the air box that houses the air filter and mounted another battery where air was mounted and wired it to the original battery in parallel , then there was 6.5 volts at the coil when the starter was running and the motor started instantly ..i will be making a new air box for the air filter that mounts on the carbs to the battery box

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