1991 GSXR 750 issue - Suzuki GSX-R Motorcycle Forums Gixxer.com
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post #1 of 11 (permalink) Old 07-07-2019, 06:45 PM Thread Starter
Squid
 
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1991 GSXR 750 issue

Hi all

I am new to Gixxer.com, however I regularly look for info without having logged in. Anywho, I have purchased a lovely 1991 GSXR 750 and it has been sweet as (absent having to helicoil the sump plug).

I have now run into another issue. Basically, every time I give it hard throttle (regardless of what gear the bike is in) the whole bike shakes and makes a loud clank noise .

Is this a gearbox rebuild, or could it be the front sprocket and chain being too loose?

Any help would be legit.

Cheers from NZ
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post #2 of 11 (permalink) Old 07-08-2019, 02:00 AM
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Re: 1991 GSXR 750 issue

Hi from NZ as well.

Your chain at the midpoint should move when pushed 1.5 inches or 38 mm - https://www.cycleworld.com/2015/08/2...orcycle-chain/
This is a ballpark.

If its not the chain (which I suspect its not) don't give it anymore hard throttle. It is going to be a major
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post #3 of 11 (permalink) Old 07-08-2019, 05:43 PM
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Re: 1991 GSXR 750 issue

As I read your post and when you began by saying "the whole bike shakes" on WOT regardless of gear, at first I thought you might be dealing with a fuel delivery issue through the mains, but then later when you mention "clank", I became concerned that it is either something other than your chain and more serious or a combination of more than one thing going on.


Is it possible that at WOT the bike is shuddering because the fuel delivery circuit through one or more of the carbs is dirty and the bike is shaking/sputtering because of that and therefore the loose chain is clanking around in response to a very disruptive fuel flow? In the past, I have had such an issue with the bike shaking under WOT in any gear and it was indeed a carb issue that was resolved with a cleaning/rebuild. Since your bike is new to you and the condition and history of the carb maintenance may not be known, I bring this possibility up as a potential issue contributing to your situation because the shuddering sounds very similar to what I experienced, although I did not have any clanking. Therefore you may have two things going on here.



As mentioned already, check and/or adjust your chain to specs including inspecting the condition of both sprockets. If there is no adjustment or replacements necessary, it is likely not the chain clanking around. If the chain was very loose or the sprockets needed replacement, test ride the bike again and see what is happening. If the shuddering still causes a clank, then it is likely inside the cases. However, the shuddering cause still needs to to be resolved and ensuring that the fuel delivery system is not being restricted at WOT is your next thing to look into and correct if necessary. Once that is established, test ride the bike again. If you are still getting a shuddering and/or clank or just now the clank, then I'm afraid you have a serious issue within the cases that likely warrants the bike inoperable until the issue is resolved by splitting the cases and inspecting everything.


During these test rides, a clank that is coming from within the cases is serious and may be dangerous and catastrophic. Please be careful and once you hear that noise, immediately slow down and nurse the bike back home.



Good luck,
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post #4 of 11 (permalink) Old 07-08-2019, 09:16 PM Thread Starter
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Re: 1991 GSXR 750 issue

Cheers both for the info.

I will check the sprockets and chain this eve and give an update. I am going to assume its a major, that way anything less is a bonus
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post #5 of 11 (permalink) Old 07-09-2019, 04:28 PM Thread Starter
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Re: 1991 GSXR 750 issue

Here is a photo of the sprocket. As you can see it is chipped and some of the teeth have completely. Not 100% if this is a cause or a symptom of the clang noise.

I rode it and looked at it when pulling throttle quickly to WOT and the sprocket appears to stop momentarily.

Will replace chain and both sprockets and see how that goes.

Cheers
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post #6 of 11 (permalink) Old 07-10-2019, 01:02 AM
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Re: 1991 GSXR 750 issue

Fark that sprocket is shot to hell.

Your chain has been jumping and rolling over the teeth, damn lucky it hasnt broke and caused you a serious crash
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post #7 of 11 (permalink) Old 07-10-2019, 01:24 AM
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Re: 1991 GSXR 750 issue

Wow!!! You've found most, if not all of your issue.

On a slightly different topic, and if you're looking for this sort of improvement, don't forget to take advantage of the opportunity to change your gearing at this time since you are changing out the chain and sprockets. Others, here may weigh in with their opinions regarding this subject and since I'm an 1100 oiler owner, I don't have an opinion or experience with your 750 bike, specifically. However, for my experience with my '89 1100, '96 750, '02 1000 and '07 750, I really was/am pleased with a 1 down, 2 up combination in gearing change. The track bikes were sometimes changed to a 520 chain but usually I kept the heavier OEM 530/525 chain for durability and longevity. Quite frankly, and especially on the street, the 520 conversion you may hear others swear by (and likely from those who are innocently/ignorantly repeating what they've heard through gossip), is not all it's cracked up to be.

I'm glad you've made progress in finding your issue and hopefully this leads you away from a more serious condition as first feared.

Cheers,


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"The price of freedom is eternal vigilance." Thomas Jefferson
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post #8 of 11 (permalink) Old 07-10-2019, 04:25 PM Thread Starter
Squid
 
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Re: 1991 GSXR 750 issue

Thanks guys. I am hoping that this is the problem. Very lucky the chain didnt jump off.

Also, noted on the gearing and the chain size, that seems a pretty reasonable suggestion and durability is def my focus at the moment (until i win Lotto or something).

Now that I am looking for a chain and sprocket kit - any suggestions as to which website is best to purchase from, bearing in mind I am in New Zealand. Maybe KiwiSuzuki1100 can help out?

Thanks
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post #9 of 11 (permalink) Old 07-11-2019, 01:21 AM
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Re: 1991 GSXR 750 issue

Yup - Just ebay it - oodles of options
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post #10 of 11 (permalink) Old 07-13-2019, 12:26 AM
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Re: 1991 GSXR 750 issue

I just use the local Suzuki dealer for my parts, sometimes cheaper than ebay and if its not right you can return it
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post #11 of 11 (permalink) Old 07-16-2019, 02:50 PM
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Re: 1991 GSXR 750 issue

yeah, that front sprocket is wasted!

i'd suggest running a 520 chain/sprocket. helps with performance while reducing weight. i've been running a 520 set up on my first gen 750's for almost 15 years without issue...and on the track as well.

good luck and keep us updated.
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