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Discussion Starter #1
Hello guys (Sorry for my poor English skills).

After reading a million threads in here and discovered that here are some very talented people, I hope there are some of you guys who might help me out here.
I have recently purchased a Honda CBR 900RR 1995 model SC28 which has been installed with a newer 1999 SC33 engine.

My problem is that the bike drives like crap between idle and 4K rpm. The engine is making a loud ticking/knocking/sputtering noise (really hard to explain) during heavy acceleration, and it has a lack of power too. The bike does this only between idle and exactly 4k rpm, in all gears, but only under heavy load (more than half throttle). After 4k rpm the bike takes off like a rocket and drives like a dream without any noises at all.
I have had the bike at tree difference mechanics , and none of them could tell what is wrong. only guesses like valve adjustments, wrong ignition timing, worn main bearings,

I have made these things recently:
The cylinder head has been removed and everything is measured and checked. Everything looked very fine. New head gasket, and the head are on again.
I have checked the chain tensioner and the cam chain guides which look pretty much like new and work fine.
The valves are adjusted.
Change the old 1995 sc28 CDI Box a SC33 1999 model.
Carburetor cleaned and synchronized.


Despite this the noise and lack of power remain the sameL

However; I just noticed that the carburetor is the old SC28 1995 model which is without TPS.
Before I spend a lot of $ on a new sc33 carburetor whit TPS I would like to hear your opinion. How do a Blade sc33 runs if you unplug the TPS? Is it possible that this is the problem or should I look elsewhere for this problem?


I really hope to solve this problem soon.
 

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My old sc33 ran fine without tps sensor but I was also using 95harness on 97sc33.
id look into the carbs again at brass nipple behind black covers on mouth of carbs check idle circuits out blow with compressed air.
 

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My problem is that the bike drives like crap between idle and 4K rpm. The engine is making a loud ticking/knocking/sputtering noise (really hard to explain) during heavy acceleration, and it has a lack of power too. The bike does this only between idle and exactly 4k rpm, in all gears, but only under heavy load (more than half throttle). After 4k rpm the bike takes off like a rocket and drives like a dream without any noises at all.

This sounds perfectly normal to me.
Don't try to accelerate below 4000RPM, the engine is not designed to breathe that low.
The noise you are describing is detonation and will destroy the pistons if you keep doing it.
 

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I can lug mine in third low rpm 2-3k 30mph-20mph and kinda chugs dont make bad noises tho. zero take off if that's what your describeing.
Bladeracer is right! These engines aren't designed to run low rpms. Much happier mid range/high rpms.
when I was tinkering with my carbs after rebuild did experience cluncky knocks. carbs fully tore down needing further sync and tuneing. Shes nice now. Id look further in carb sync or clogged carb somewhere idle circuit. Easy to miss that 1. Lol been there.
 

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Discussion Starter #5
This sounds perfectly normal to me.
Don't try to accelerate below 4000RPM, the engine is not designed to breathe that low.
The noise you are describing is detonation and will destroy the pistons if you keep doing it.


By detonation do you mean that the mixture is igniting too early?

But this problem is hardly at all CBR SC33 models? I can understand that the engine must have some rpm before it take off, but It also do this in 1.gear, however in some smaller degree, but still I can’t give full throttle without the noise and lack of power. Can’t believe it is supposed to do like that.
If I give a little too much throttle at low rpm is really sounds like the engine if falling apart (Slapping/nocking/spluttering noise). Everything over 4000 rpm and the bike runs just perfect without any noises at all.

Is there anything you can do about this? Should a gasoline with a higher octane number be able to take care of such at problem? I have tried this, but the problem remains unchanged. Or could it help to retarded ignition timing a bit? For example by installing an adjustable ignition timing device?
 

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By detonation do you mean that the mixture is igniting too early?

But this problem is hardly at all CBR SC33 models? I can understand that the engine must have some rpm before it take off, but It also do this in 1.gear, however in some smaller degree, but still I can’t give full throttle without the noise and lack of power. Can’t believe it is supposed to do like that.
If I give a little too much throttle at low rpm is really sounds like the engine if falling apart (Slapping/nocking/spluttering noise). Everything over 4000 rpm and the bike runs just perfect without any noises at all.

Is there anything you can do about this? Should a gasoline with a higher octane number be able to take care of such at problem? I have tried this, but the problem remains unchanged. Or could it help to retarded ignition timing a bit? For example by installing an adjustable ignition timing device?

Have you ridden other bikes that allow you to use hard throttle from low rpm?
I can't even think of any situation where you would be riding at such low rpm and want to accelerate hard. Even a "normal" launch on the road would barely drop under 4000rpm. A "hard" launch would probably be closer to 6000rpm, and a "race" launch would be closer to 8000rpm.
 

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Discussion Starter #7
Have you ridden other bikes that allow you to use hard throttle from low rpm?
I can't even think of any situation where you would be riding at such low rpm and want to accelerate hard. Even a "normal" launch on the road would barely drop under 4000rpm. A "hard" launch would probably be closer to 6000rpm, and a "race" launch would be closer to 8000rpm.
I know that no bike likes hard throttle from low rpm, but I have never ridden a bike that had this bad sound under hard throttle. There is clearly something wrong. It is hard to describe the sound, but had a test ride today without the tank and air filter and the sound is clearly coming from the top end, and can be heard very loud through the carburetor.
I do not normally use hard throttle with low rpm, but I have to start and stop the bike and every time I start/accelerates under 4000 rpm the bike sounds like I is going to die. And I have to reach 4000 rpm somehow.
I have come to a spot where I have no clue where to look at the problem. Have spent a couple of hours playing and adjusting the carbs (again). This didn’t change anything according to the problem.
 

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I know that no bike likes hard throttle from low rpm, but I have never ridden a bike that had this bad sound under hard throttle. There is clearly something wrong. It is hard to describe the sound, but had a test ride today without the tank and air filter and the sound is clearly coming from the top end, and can be heard very loud through the carburetor.
I do not normally use hard throttle with low rpm, but I have to start and stop the bike and every time I start/accelerates under 4000 rpm the bike sounds like I is going to die. And I have to reach 4000 rpm somehow.
I have come to a spot where I have no clue where to look at the problem. Have spent a couple of hours playing and adjusting the carbs (again). This didn’t change anything according to the problem.

You _never_ "need to reach 4000rpm" by using hard throttle.
Have you ridden similar bikes though, other 900RR's for example or GSXR750's?
I have to launch my bikes as well, but if I have to crawl along in the bottom third of the tach for some reason I won't ask it to accelerate hard while I'm down there, get the revs up and then accelerate.
You said it's not a problem at less than half throttle, which definately sounds like detonation to me.
Stop riding it this way, there is no reason at all to do this to your engine.
 

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Discussion Starter #9
You _never_ "need to reach 4000rpm" by using hard throttle.
Have you ridden similar bikes though, other 900RR's for example or GSXR750's?
I have to launch my bikes as well, but if I have to crawl along in the bottom third of the tach for some reason I won't ask it to accelerate hard while I'm down there, get the revs up and then accelerate.
You said it's not a problem at less than half throttle, which definately sounds like detonation to me.
Stop riding it this way, there is no reason at all to do this to your engine.
I have driven GSXR750 1989, FZR 1000 1988, YZF 1000 1996, ZX10 1990, vfr1995. None of them did anything similar to this.
I wish we were closer to each other them I would come by to let you have a ride and listen to it. It is indeed very hard to explain how the engine sounds and probably even harder to figure out what is wrong without having the bike with you. All my respect to you for spending your time answering my post.
Believe me there is something wrong. Even an engine of a Blade must not make a sound like that, and the lack of power is too much to be within an acceptable limit. Another thing that seems odd to me is that at EXACTLY 4000 RPM the bike change to run perfect in all gears.

I started this other thread but don’t know if this has anything to do with this problem
 

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I have driven GSXR750 1989, FZR 1000 1988, YZF 1000 1996, ZX10 1990, vfr1995. None of them did anything similar to this.
I wish we were closer to each other them I would come by to let you have a ride and listen to it. It is indeed very hard to explain how the engine sounds and probably even harder to figure out what is wrong without having the bike with you. All my respect to you for spending your time answering my post.
Believe me there is something wrong. Even an engine of a Blade must not make a sound like that, and the lack of power is too much to be within an acceptable limit. Another thing that seems odd to me is that at EXACTLY 4000 RPM the bike change to run perfect in all gears.

I started this other thread but don’t know if this has anything to do with this problem

All of those bikes except for the GSXR are known for their strong midrange.
You need to find somebody with another 900RR you can test ride.
Or, since you admit it rides just fine above 4000RPM, simply stop riding the bike this way - it clearly does not like it and there is no reason to punish it like this.
 

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Recheck your timing. But don't think its there.
I had similar nasty noises shortly after carb overhauls. Had Lil bugger in one carb got out it fixed then resynced carbs. While I was syncing it still made bad rattle banging noises hiccuping around. But ran great higher rpms.
continued to fiddle with fine tuneing the carbs and syncing. Problem solved.
If ur sure its not timing, loose valve lifters, its gonna be in your carbs. Weather uve done them or not.
it shouldn't be the way you describe.
are you sure you timing chain guides installed properly and that one is snugged up coming from backside of head by thermostat?
What u are describing make me think mis tuned carbs even if it runs decent out top higher rpms.
ReCheck your carbs with tip cleaners for torch. And bench sync your. Carbs before you sync them. Start with throttle flaps almost full closed. 3-4 then 1-2 then 2-3 back to 3-4 again 1-2 back to 2-3. Numerous times till hers bout perfect. You will also constantly adjust idle to keep the same.
 

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Recheck your timing. But don't think its there.
I had similar nasty noises shortly after carb overhauls. Had Lil bugger in one carb got out it fixed then resynced carbs. While I was syncing it still made bad rattle banging noises hiccuping around. But ran great higher rpms.
continued to fiddle with fine tuneing the carbs and syncing. Problem solved.
If ur sure its not timing, loose valve lifters, its gonna be in your carbs. Weather uve done them or not.
it shouldn't be the way you describe.
are you sure you timing chain guides installed properly and that one is snugged up coming from backside of head by thermostat?
What u are describing make me think mis tuned carbs even if it runs decent out top higher rpms.
ReCheck your carbs with tip cleaners for torch. And bench sync your. Carbs before you sync them. Start with throttle flaps almost full closed. 3-4 then 1-2 then 2-3 back to 3-4 again 1-2 back to 2-3. Numerous times till hers bout perfect. You will also constantly adjust idle to keep the same.

Throttle synch plays very little if any role in any throttle openings much higher than idle speed. The microscopic adjustments to synch the throttle plates have no relevance when the throttle plates are open.
 

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Iv seen them run bad low and good in higher rpms. From mistuned carbs.
what your describeing is in no way normal. And definately should not be out riding trying to make it run around clunking and banging.
Exhaust all avenues tuneing and cleaning! Quit riding till its fixed. Won't be worth a damn with broken con rod or something!

What did you tune your carbs with?
 

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Something else that will exacerbate it is if you've raised your gearing.
 

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It sure does bladeracer,
put 1/8 twist on one or two barely open throttle and you'll watch the air op slides bouncing up and down irregularly. Run like **** down low and fine up top.
 

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What he is decsribeing is coming from idle circuit/or mistuned synced carbs.
Says horrible down low and carb sync haveing different vacuum pulls on each carb would cause fluttering hiccups and bad noises. Definately looking into some more!
 

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It sure does bladeracer,
put 1/8 twist on one or two barely open throttle and you'll watch the air op slides bouncing up and down irregularly. Run like **** down low and fine up top.

We're not talking about slight throttle.

From Post#1:
"The bike does this only between idle and exactly 4k rpm, in all gears, but only under heavy load (more than half throttle)."
 

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Discussion Starter #18
Recheck your timing. But don't think its there.
I had similar nasty noises shortly after carb overhauls. Had Lil bugger in one carb got out it fixed then resynced carbs. While I was syncing it still made bad rattle banging noises hiccuping around. But ran great higher rpms.
continued to fiddle with fine tuneing the carbs and syncing. Problem solved.
If ur sure its not timing, loose valve lifters, its gonna be in your carbs. Weather uve done them or not.
it shouldn't be the way you describe.
are you sure you timing chain guides installed properly and that one is snugged up coming from backside of head by thermostat?
What u are describing make me think mis tuned carbs even if it runs decent out top higher rpms.
ReCheck your carbs with tip cleaners for torch. And bench sync your. Carbs before you sync them. Start with throttle flaps almost full closed. 3-4 then 1-2 then 2-3 back to 3-4 again 1-2 back to 2-3. Numerous times till hers bout perfect. You will also constantly adjust idle to keep the same.
I have just done all that two weeks ago. I am very certain that the carbs are tuned to where they need to be. I test ride the bike a lot of times under the fine tuning and the sound was stile the sameL
Could this sound be the crankshaft bearings or piston bearings, piston rings?
 

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Discussion Starter #19
All of those bikes except for the GSXR are known for their strong midrange.
You need to find somebody with another 900RR you can test ride.
Or, since you admit it rides just fine above 4000RPM, simply stop riding the bike this way - it clearly does not like it and there is no reason to punish it like this.


It maybe sounds like I am forcing the bike to do heavy pulling on low rpm but I don’t. This is only to explain when the sound occurs. I ride the bike like most of us would on the street, and when sometime the rpm gets under 4000rpm, and it dos, then we have the bad sound. Again thanks for spending time on my bike, bud don’t tell me that Honda build a bike that is unable to run when given more than ½ throttles at lower rpm than 4000! I am not doing this all the time, but when it happens the bike shall not sound like it is going to die! So please enough of that it is supposed to sound like that, It isn’t. nobody would by a new bike with a sound like that.
 

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We're not talking about slight throttle.

From Post#1:
"The bike does this only between idle and exactly 4k rpm, in all gears, but only under heavy load (more than half throttle)."
How the hell can he be at (more then half throttle) and at or under 4k rpms??? 6th gear 10mph? Lmao going up 30° incline???
if that's case no wonder he says runs like crap.
 
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