Throttle Problem, Maybe....

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Throttle Problem, Maybe....

Bud Izen
On my last long trip (to Colorado) I experienced something new in the
way of a trouble symptom. It was a pretty high speed trip, unlike any
other one I had ever undertaken. I rarely use WOT so when I had occasion
to use it, it seemed like the throttle would run out of
counter-clockwise rotation before the carbs would open up. The bike
acted like it always did, up to about 80mph, but when I wanted to open
it up, it would slowly increase in speed. Eventually it would reach 90,
95, 100 but it was more gradual than I would have liked. The other thing
I noticed was that my gas mileage was not up to par. Now, I know that
when the average speed gets much higher than 70, that mileage will
decrease, so I don't pay much attention to mpg when going fast on the
freeway. When I was on back roads, though, my mileage is usually 45mpg.
Over the entire time I have had the bike, ever since I did my first carb
balance, I always get at least 45mph.

The other thing I finally noticed on my second to last day was that when
I was going around 80 and wanted to go faster, I could rotate the
throttle more, but what I found was that, to my surprise, it was at full
rotation. I would say WOT, but it didn't feel like WOT in terms of the
bike's behavior.

On my most recent trip to California (the Bay Area and then Yosemite), I
got rained on on every single mile of I-5 and most of the rest of the
600 mile first day. Needless to say, I wasn't breaking any land speed
records. I don't think I went faster than 70 the entire trip down, and
most of the time slower than that. 40mpg.

So, I started thinking about what could cause this and I came to a few
conclusions. First, the carbs had not been balanced in over a year.
Then, the valves are about due to be checked. The spark plugs are
Iridium and are still plenty good, although I may take them out to see
if the bike is running rich. Then there is the air box and air filter.

This week, today in fact, I started stripping down the bike to have a
look at all those things. I had done the airbox mod a few years ago, so
taking the air filter out was no big deal. It was filthy. I believe this
was actually only the third air filter since it was new. Once I had made
the airbox mod, I found you could clean and reuse the stock filter, so
that's what I did, twice. Anyway, I think this one looks like it doesn't
owe me anything, so I ordered a K&N. It wasn't particularly cheap but
$55 is better than $80, plus K&N indicate that you never have to replace
the filter ever again. We'll see. At any rate, the condition of the air
filter no doubt contributed to the decreased gas mileage. My guess is
that the mileage problem will be totally remedied by new air filter and
carb balance. But neither will address the throttle issue.

While taking everything off, it occurred to me that the throttle problem
might have another cause. I thought it might be possible that the
throttle itself might be limited in rotation, so that it never has a
chance to get to WOT. So, I am  posing this question to you guys, in the
hopes that a couple of you 900 owners (I hate making assumptions, so I
don't wish to assume that the throttle range on the 1200s is the same as
on the 900s.) will measure your throttle range and let me know if your
range is greater than mine.

Here's how I measured my range. I gripped the throttle with my knuckles
even with the flat part of the brake lever. Then I rotated my hand
keeping the throttle gripped tightly. The most I could rotate my hand
was about 45 degrees. To be as descriptive as I can, I could only rotate
my hand so that, when I could not rotate it any further, it was about
half way between flat (knuckles facing brake lever) and knuckles facing
straight up (wrist bent at maximum angle). I hope that's clear. I guess
I could answer my own question if I could just recall what normal
rotation is, but I flat out do not remember. I THINK it used to rotate
more, but I figured asking you folks beats guessing.

Thanks in advance for your input and suggestions.

Bud Izen

'99 Platinum 900

Springfield Oregon


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Re: Throttle Problem, Maybe....

gandrews2
Hi Bud, I'm glad to see you're out riding. I'm not getting the long trips I used to take. Years ago I got caught for hours riding in the rain from Kansas City to Denver. As I got closer to Denver the bike wouldn't go over 90 mph. This was before I installed a Scottoiler, I was using some chain lube in a spray can. I'd lube up the chain every other gas stop. Apparently the chain didn't get enough lube during the rain. When I got to Calif. at my brother house we looked at the chain. Lots of kinks and not flexible. I bought a new chain and all was good. My brother soaked the chain in oil for days and it was still stiff, in the trash it went. Now when I'm in the rain I turn up the Scottoiler full blast. Oil is cheap. Another condition might be one of the vacuum slide diaphragms has a hole or a slice in it. The butterfly valves go to WOT but the slide isn't going all the way up. I'd check the throttle grip on my bike if I were at home, but I'm not, so I can't help you there. It's hard to imagine the cable going bad and not letting throttle open all the way. I doubt it being the fault of the valve clearances. Our bikes have quit a few miles on them and the valve clearances stay pretty steady. So my short list would be:  Chain or diaphragms.
 Greg Andrews
 '96 90 BRG 109,000
 runs perfect
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Re: Throttle Problem, Maybe....

Bill Bennit
In reply to this post by Bud Izen
G'day Bud, I have just checked my 98 BBBB. I have a cruise control that
clips on to the throttle and acts like a pointer, so it's easy to see
the rotation. Mine is a little less than 90 deg, maybe 85 deg eyeballing
it - 'pointer' goes from nearly horizontal to vertical.  Lots more than 45.

Autumn here - a fine week of low twenties celsius coming up, perfect.

Bill

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Re: Throttle Problem, Maybe....

Bud Izen
In reply to this post by Bud Izen
Thanks, Bill! I may have other issues, but the lack of an almost 90
degree rotation is certainly the place I am going to start. I SO
appreciate this vital info.

Thanks again, as well as to everyone who posted suggestions. When
troubleshooting anything, it is important to keep an open mind and
assume anything.

Bud


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Re: Throttle Problem, Maybe....

David Webb
Hi Bud,
If you still have the airbox open, you can check the butterfly position while turning the throttle handgrip.
Based on your description, I'm guessing that you might have something in your throttle cable or other that's keeping the bike from opening up.
I thought of some other possibilities like clogged fuel screens, bad gas, etc. but I think the symptoms don't sound right.  
If you find that your throttles open all the way, you might want to check your coils.  I'm betting on a broken strand in the throttle cable that's preventing full-range motion.
- Dave

      From: "Bud Izen [hidden email] [TriumphTrophy]" <[hidden email]>
 To: "[hidden email]" <[hidden email]>
 Sent: Monday, May 14, 2018 12:29 PM
 Subject: [TriumphTrophy] Re: Throttle Problem, Maybe....
   
    Thanks, Bill! I may have other issues, but the lack of an almost 90
degree rotation is certainly the place I am going to start. I SO
appreciate this vital info.

Thanks again, as well as to everyone who posted suggestions. When
troubleshooting anything, it is important to keep an open mind and
assume anything.

Bud


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Re: Throttle Problem, Maybe....

Bud Izen
In reply to this post by Bud Izen
Yes, David, my money, so far, is on a mechanical problem. It would seem
to be either something jammed at the twist-end, the carb end, or the
cable itself. If I can ever get beyond the necessary household stuff
that my partner and I are currently working on, I am hoping to find some
time to work on it soon. I have the bike all stripped down, but have yet
to loosen the clamps holding the filter to the carbs, so I can't see
inside just yet. Will keep you posted. Thanks for everyone's
suggestions. Oh, and btw I doubt it's coils - I replaced the originals
with Nology coils and spark plug leads a few years ago. I know what
failing coils feel like, and this does not seem like it.

Bud Izen

'99 Platinum 900

Springfield Oregon


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Re: Throttle Problem, Maybe....

David Webb
Hi Bud,
If I remember correctly, you may have done the airbox mod to split the horns of the airbox into 2 separate halves so they can be removed without unseating the carb-side of the airbox.
If so, then you can just pop out the air filter and take a look down the throats of the carbs without needing to loosen the front half of the airbox.
If not, then you will indeed need to loosen the clamps and unseat the airbox from the carbs.  Also, you'll need to loosen the clamps that seat the carbs to the cylinder heads and lower the carb assembly to remove the airbox.  While you have the airbox off, you might do the mod.  Just separate the front/rear halves of the airbox and using a hacksaw, make an off-center or slightly diagonal cut between the horns of the dirty side of the airbox.  There are pictures online at the Trophy wiki.  When you bolt it all back together, always mount the black short screws that go into the plastic before mounting the silver long screws that go into the brass inserts.
- Dave

      From: "Bud Izen [hidden email] [TriumphTrophy]" <[hidden email]>
 To: "[hidden email]" <[hidden email]>
 Sent: Saturday, May 19, 2018 11:56 AM
 Subject: [TriumphTrophy] Re: Throttle Problem, Maybe....
   
    Yes, David, my money, so far, is on a mechanical problem. It would seem
to be either something jammed at the twist-end, the carb end, or the
cable itself. If I can ever get beyond the necessary household stuff
that my partner and I are currently working on, I am hoping to find some
time to work on it soon. I have the bike all stripped down, but have yet
to loosen the clamps holding the filter to the carbs, so I can't see
inside just yet. Will keep you posted. Thanks for everyone's
suggestions. Oh, and btw I doubt it's coils - I replaced the originals
with Nology coils and spark plug leads a few years ago. I know what
failing coils feel like, and this does not seem like it.

Bud Izen

'99 Platinum 900

Springfield Oregon

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Re: Throttle Problem, Maybe....

Bud Izen
In reply to this post by Bud Izen
Thanks, Dave. I did do the air box mod some time ago. Today I removed
the back(s) of the air box but my injured thumb kept me from doing
anything further. I had already removed the throttle cable from the
twist grip so I was not able to observe the butterflies. As soon as I
can, I am going to pull the carbs off, and make sure that the carb-end
connection is not obstructed and also make sure the cable is good. I am
not getting anything like 90 degrees of rotation at the twist grip. That
being the case, it is unlikely that, if I put together everything now,
with only about 45 degrees of rotation it is a dead certainty that the
butterflies will not be opening all the way. Again, thanks for the
suggestion.

Bud Izen

'99 Platinum 900

Springfield Oregon


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