Sounds like we are having similar problems, I stripped the carbs and rebuilt with Litech (?) green seals whilst I had to swop cylinder heads after trying to get the old head off resulted in three exhaust stud stumps. I put the Factory Pro kit in my carbs too and now it doesn't run at all between 2.5k and 3.5k then by 4k it clears and takes off like a scolded cat. I've spent hours farting around with and lost patience, I think a change of carbs would solve the issue but thats an extreme solution.
You say you've tried the float level from 12 to 15, I'm assuming your talking measuring the corner of the float relative to the sealing face? Another member here (sorry to whomever but can't remember who) made a point that thats not the correct way to measure the float level, you're supposed to use a clear plastic tube from the float bowl drain and measure against the casting mark on the carb body. Its a pig to do on the bike but the only way you can be certain where your fuel level is actually. You might have to search for the thread or a kind other member knows what I'm talking about and will guide you in the right direction.
To be honest I'm amazed it works at all given the sloppy fit of the float valve to the float. Sorry I couldn't give you the information you are after, I'm about burnt out with the frustration of it all as well. Have you tried playing with the A/F mixture, if the carb has new seals the relative position of the needle will be very different to the original as the seals still have 'fatness' where as the original seals would have been squashed almost flat, so the relative effect would be very different at the same setting.
One more top end rebuild
Moderators: trixynut, Mincehead, dicky, phuk72, Jak, Kevtrx849
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Overlord Neil
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Re: One more top end rebuild
C90, TS50, H100, H100, CB250, GS500, Tiger 955i, TRX850, Tuono, ZZR600, CBR954RR
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Capau
- TRX-Enthusiast
- Posts: 24
- Joined: Sat Jan 28, 2017 10:11 am
- Location: Russia
Re: One more top end rebuild
Well, talking about fuel level, I did meazure it with clear tubes. Once at the very begining. And It showed more or less the correct reading regarding the mark on carb body. You know, that it's hard to make some accurate measurements there. After that I checked the level of the float. And it showed 14mm exactly. After that just for an accurate experiment I tried several levels (12,13,15) with no difference to bike behavior at all. The only thing that works fine is to remove the airbox.
All my seals are old, but they look fat enough to seal.
I 've turned the mixture screw half a turn from standart 2.5 and nothing changed.
All my seals are old, but they look fat enough to seal.
I 've turned the mixture screw half a turn from standart 2.5 and nothing changed.
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Capau
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Re: One more top end rebuild
And I guess we have different promlems at the end. I would say, that up to 3.5k rpm the engine works more like fine. Then at 4000 there is an awful flat spot and at any rpm over 3.5k there is a problew when twisting the throttle fast.
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Overlord Neil
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Re: One more top end rebuild
I replaced the inlet boots, mine were likewise cracked but 'looked' ok, the new boots have made a difference, I now have a solid bog and stutter at 3k rpm then she takes off. I might replace the fuel pump and vacuum lines and see if that makes a difference.
C90, TS50, H100, H100, CB250, GS500, Tiger 955i, TRX850, Tuono, ZZR600, CBR954RR
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Overlord Neil
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Re: One more top end rebuild
Internet rumaging I found the Factory Pro guide (which I lost):
Follow steps in order....First, dial in:
1. Top end (full throttle / 7.5k to redline -
Best Main Jet must be selected before starting step 2 (needle height)!
Select Best Main Jet
To get the best, most even top end power (full throttle/after 7500 rpm), select the main jet that produces the hardest pull at high rpm.
If the bike pulls harder at high rpm when cold and less hard when fully warmed up, the main jet is too large. Install a smaller main jet and retest until you find the main jet that pulls the hardest at high rpm when fully warmed up. This must be done first - before moving on to the other tuning ranges.
If the bike doesn't pull well at high rpm when cold and gets only slightly better when fully warmed up, the main jet is too small.
In order to properly tune the midrange and low rpm carburetion, THE MAIN JET MUST FIRST BE PROPERLY SELECTED after 10 to 15 minutes of hard use!
Do not pay too much attention to the low-end richness when you are changing main jets - you still need to be using the main jets that produce the best power at high rpm. You will deal with the low-end / cruise later - after step 2.
2. Midrange (full throttle /5k-7k)
Step 1 (Best Main Jet) must be selected before starting step 2!
Select best needle clip position
To get the best power at full throttle / 5k-7k rpm, adjust the needle height, after you have already selected the best main jet.
If the engine pulls better or is smoother at full throttle/5k-7k in a full throttle roll-on starting at <3k when cool but soft and/or rough when at full operating temperature, it is too rich in the midrange and the needle should be lowered.
If the engine pulls better when fully warmed up but still not great between 5k-7k, try raising the needle to richen 5k-7k.
If the engine pulls equally well between 5k-7k when cooler as compared to fully warmed up, the needle height is probably properly set.
Do not pay too much attention to the low-end richness when you are changing needle clip positions - you still need to be using the clip position that produces the best full throttle / 5k-7k power in conjunction with the main jets (Step 1) that produce the best power at high rpm. You will deal with the low-end / cruise next.
3. Low end (full throttle / 2k-3k)
Step 1 (Best Main Jet) and Step 2 (needle height) must be selected before starting step 3!
Float height (AKA fuel level & how to..)
To get best low-end power, set float height (fuel level) so that the engine will accept full throttle, without missing or stumbling, in 2nd gear from 2.5k to 3k rpm at minimum.
Float heights, unless otherwise specified in the installation guide, are measured from the "gasket surface" of the carb body to the highest part of the top of the float - with the float tang touching but not compressing the float valve spring.
If the engine has a "wet" rhythmic, soggy area at full throttle / 3k-4k rpm, that gets worse as the engine heats up, lower the fuel level by resetting the float height 1mm greater (if the original was 13mm - go to 14mm). This will lower the fuel level, making full throttle / 2k-3k rpm leaner.
If the engine is "dry" and flat between 2k to 3k rpm, raise the fuel level.
Example: change float height from 15mm to 14mm to richen up that area.
REMEMBER, since the main jet WILL affect low speed operation, the MAIN JET has to be within 1 or 2 sizes of correct before final float setting.
Warning: If the engine is left with the fuel level too high,, the engine may foul plugs on the street and will be "soft" and boggy at part throttle operation. Adjust Floats to raise/ lower the Fuel Level.
Base settings are usually given if a particular application has a history of fuel level criticalness. The Fuel level height in the float bowl affects full throttle/low rpm and, also, richness or leanness at cruise/low rpm.
Reference: a bike that runs cleanly at small throttle openings when cold, but starts to show signs of richness as it heats up to full operating temperature, will usually be leaned out enough to be correct if the fuel level is LOWERED 1mm. Check out and RESET all: Suzuki (all), Yamaha (all) and Kawasaki (if low speed problems occur). Needless to say, FUEL LEVEL IS EXTREMELY IMPORTANT!!!
If there are low-end richness problems, even after lowering the fuel level much more than 1.5mm from our initial settings, check for needle wear and needle jet (part of the emulsion tube). See Worn Needle and Worn Needle Jet diagram. It is VERY common for the brass needle jets (in the top of the "emulsion tube") in 36mm, 38mm and 40mm Mikuni CV carbs to wear out in as little as 5,000 miles. Check them for "oblong" wear - the needle jet orifice starts out round! Factory Pro produces stock replacement needle jets / emulsion tubes for 36mm and 38mm Mikuni carbs. Click here
4. Idle and low rpm cruise
Fuel Screw setting (AKA mixture screws)
There is usually a machined brass or aluminum cap over the fuel screws on all but newer Honda. It's about the diameter of a pencil. Cap removal details. Newer Honda carbs have no caps, but use a special "D" shaped driver, usually supplied in the carb recal kit. We do have them available separately, too. 800 869-0497 to order -
Set for smoothest idle and 2nd gear, 4k rpm, steady state cruise operation. Set mixture screws at recommended settings, as a starting point. For smoothest idle, 2nd gear 4000 rpm steady state cruise , and 1/8 throttle high rpm operation. (pj tuning information)
Pilot fuel mixture screw settings, float level (but, you've "fixed" the fuel level in Step 3 - which you have already done!) AND pilot jet size are the primary sources of mixture delivery during 4000 rpm steady state cruise operation.
If lean surging is encountered, richen mixture screws (turn out) in 1/2 turn increments. Alternative pilot jets are supplied when normally required.
Pilot fuel mixture screw settings, float level and pilot jet size also affect high-rpm, 0 to 1/8 throttle maneuvers. Too lean, will cause surging problems when the engine is operated at high rpm at small throttle openings! Opening the mixture screws and/or increasing pilot jet size will usually cure the problem.
NOTE: A rich problem gets worse as the engine heats up.
If the throttle is lightly "blipped" at idle, and the rpm drops below the set idle speed, then rises up to the set idle speed, the low speed mixture screws are probably set too rich: try 1/2 turn in, to lean the idle mixture.
NOTE: A lean problem gets better as the engine heats up.
If the throttle is lightly "blipped" at idle, and the rpm "hangs up" before dropping to the set idle speed, and there are no intake leaks and the idle speed is set at less than 1000 rpm, the mixture screws are probably too lean: try 1/2 turn out, to richen mixture. Be sure there are no intake leaks and the idle speed is set at less than 1000 rpm!
Follow steps in order....First, dial in:
1. Top end (full throttle / 7.5k to redline -
Best Main Jet must be selected before starting step 2 (needle height)!
Select Best Main Jet
To get the best, most even top end power (full throttle/after 7500 rpm), select the main jet that produces the hardest pull at high rpm.
If the bike pulls harder at high rpm when cold and less hard when fully warmed up, the main jet is too large. Install a smaller main jet and retest until you find the main jet that pulls the hardest at high rpm when fully warmed up. This must be done first - before moving on to the other tuning ranges.
If the bike doesn't pull well at high rpm when cold and gets only slightly better when fully warmed up, the main jet is too small.
In order to properly tune the midrange and low rpm carburetion, THE MAIN JET MUST FIRST BE PROPERLY SELECTED after 10 to 15 minutes of hard use!
Do not pay too much attention to the low-end richness when you are changing main jets - you still need to be using the main jets that produce the best power at high rpm. You will deal with the low-end / cruise later - after step 2.
2. Midrange (full throttle /5k-7k)
Step 1 (Best Main Jet) must be selected before starting step 2!
Select best needle clip position
To get the best power at full throttle / 5k-7k rpm, adjust the needle height, after you have already selected the best main jet.
If the engine pulls better or is smoother at full throttle/5k-7k in a full throttle roll-on starting at <3k when cool but soft and/or rough when at full operating temperature, it is too rich in the midrange and the needle should be lowered.
If the engine pulls better when fully warmed up but still not great between 5k-7k, try raising the needle to richen 5k-7k.
If the engine pulls equally well between 5k-7k when cooler as compared to fully warmed up, the needle height is probably properly set.
Do not pay too much attention to the low-end richness when you are changing needle clip positions - you still need to be using the clip position that produces the best full throttle / 5k-7k power in conjunction with the main jets (Step 1) that produce the best power at high rpm. You will deal with the low-end / cruise next.
3. Low end (full throttle / 2k-3k)
Step 1 (Best Main Jet) and Step 2 (needle height) must be selected before starting step 3!
Float height (AKA fuel level & how to..)
To get best low-end power, set float height (fuel level) so that the engine will accept full throttle, without missing or stumbling, in 2nd gear from 2.5k to 3k rpm at minimum.
Float heights, unless otherwise specified in the installation guide, are measured from the "gasket surface" of the carb body to the highest part of the top of the float - with the float tang touching but not compressing the float valve spring.
If the engine has a "wet" rhythmic, soggy area at full throttle / 3k-4k rpm, that gets worse as the engine heats up, lower the fuel level by resetting the float height 1mm greater (if the original was 13mm - go to 14mm). This will lower the fuel level, making full throttle / 2k-3k rpm leaner.
If the engine is "dry" and flat between 2k to 3k rpm, raise the fuel level.
Example: change float height from 15mm to 14mm to richen up that area.
REMEMBER, since the main jet WILL affect low speed operation, the MAIN JET has to be within 1 or 2 sizes of correct before final float setting.
Warning: If the engine is left with the fuel level too high,, the engine may foul plugs on the street and will be "soft" and boggy at part throttle operation. Adjust Floats to raise/ lower the Fuel Level.
Base settings are usually given if a particular application has a history of fuel level criticalness. The Fuel level height in the float bowl affects full throttle/low rpm and, also, richness or leanness at cruise/low rpm.
Reference: a bike that runs cleanly at small throttle openings when cold, but starts to show signs of richness as it heats up to full operating temperature, will usually be leaned out enough to be correct if the fuel level is LOWERED 1mm. Check out and RESET all: Suzuki (all), Yamaha (all) and Kawasaki (if low speed problems occur). Needless to say, FUEL LEVEL IS EXTREMELY IMPORTANT!!!
If there are low-end richness problems, even after lowering the fuel level much more than 1.5mm from our initial settings, check for needle wear and needle jet (part of the emulsion tube). See Worn Needle and Worn Needle Jet diagram. It is VERY common for the brass needle jets (in the top of the "emulsion tube") in 36mm, 38mm and 40mm Mikuni CV carbs to wear out in as little as 5,000 miles. Check them for "oblong" wear - the needle jet orifice starts out round! Factory Pro produces stock replacement needle jets / emulsion tubes for 36mm and 38mm Mikuni carbs. Click here
4. Idle and low rpm cruise
Fuel Screw setting (AKA mixture screws)
There is usually a machined brass or aluminum cap over the fuel screws on all but newer Honda. It's about the diameter of a pencil. Cap removal details. Newer Honda carbs have no caps, but use a special "D" shaped driver, usually supplied in the carb recal kit. We do have them available separately, too. 800 869-0497 to order -
Set for smoothest idle and 2nd gear, 4k rpm, steady state cruise operation. Set mixture screws at recommended settings, as a starting point. For smoothest idle, 2nd gear 4000 rpm steady state cruise , and 1/8 throttle high rpm operation. (pj tuning information)
Pilot fuel mixture screw settings, float level (but, you've "fixed" the fuel level in Step 3 - which you have already done!) AND pilot jet size are the primary sources of mixture delivery during 4000 rpm steady state cruise operation.
If lean surging is encountered, richen mixture screws (turn out) in 1/2 turn increments. Alternative pilot jets are supplied when normally required.
Pilot fuel mixture screw settings, float level and pilot jet size also affect high-rpm, 0 to 1/8 throttle maneuvers. Too lean, will cause surging problems when the engine is operated at high rpm at small throttle openings! Opening the mixture screws and/or increasing pilot jet size will usually cure the problem.
NOTE: A rich problem gets worse as the engine heats up.
If the throttle is lightly "blipped" at idle, and the rpm drops below the set idle speed, then rises up to the set idle speed, the low speed mixture screws are probably set too rich: try 1/2 turn in, to lean the idle mixture.
NOTE: A lean problem gets better as the engine heats up.
If the throttle is lightly "blipped" at idle, and the rpm "hangs up" before dropping to the set idle speed, and there are no intake leaks and the idle speed is set at less than 1000 rpm, the mixture screws are probably too lean: try 1/2 turn out, to richen mixture. Be sure there are no intake leaks and the idle speed is set at less than 1000 rpm!
C90, TS50, H100, H100, CB250, GS500, Tiger 955i, TRX850, Tuono, ZZR600, CBR954RR
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Capau
- TRX-Enthusiast
- Posts: 24
- Joined: Sat Jan 28, 2017 10:11 am
- Location: Russia
Re: One more top end rebuild
Read the factorypro instruction above for maybe 10 times. This doesn't help. I've done all the manipulations with no difference to lag at 4000.
Put back the original needles and tubes, top end got fine, but the problem at 4000 is stil there. And it runs 8liters/100km whitch is more than a car.
I'm going to order the original tubes and needles, but I doubt that it helps.
Started smoking cigaretts. Can't stand the whole situation.
Put back the original needles and tubes, top end got fine, but the problem at 4000 is stil there. And it runs 8liters/100km whitch is more than a car.
I'm going to order the original tubes and needles, but I doubt that it helps.
Started smoking cigaretts. Can't stand the whole situation.
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dicky
- Site Sponsor / Administrator
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Re: One more top end rebuild
You may have already done this, swap out the FP needle for the original needle, keep the FP tubes.
Myself and others have found the needle supplied by FP to be rubbish. I was having similar issues to you and ditching the FP needle made everything better.
Myself and others have found the needle supplied by FP to be rubbish. I was having similar issues to you and ditching the FP needle made everything better.
dicky
OOOSDC #5
OOOSDC #5
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Capau
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- Location: Russia
Re: One more top end rebuild
Tried this. Even worse. I start to think that problem is somewhere else. Need to find a donor.
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cobbadiggabuddyblooo
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- Joined: Thu Aug 28, 2008 9:19 am
- Location: Brisbane,Australia
Re: One more top end rebuild
What fuel are you running.
One forum member I sold an IGNITECH ignition to was having similar issues.
Turned out he was using a low octane 91 RON fuel and the advanced ignition settings under 4000rpm on the IGNITECH program was the issue. As soon as he ran 95 or 98 RON fuel he stopped the detonation problem. Check there is no water in the fuel too...
One forum member I sold an IGNITECH ignition to was having similar issues.
Turned out he was using a low octane 91 RON fuel and the advanced ignition settings under 4000rpm on the IGNITECH program was the issue. As soon as he ran 95 or 98 RON fuel he stopped the detonation problem. Check there is no water in the fuel too...
laughter is the best medicine
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Capau
- TRX-Enthusiast
- Posts: 24
- Joined: Sat Jan 28, 2017 10:11 am
- Location: Russia
Re: One more top end rebuild
Thanks, Cobba.
I'm running 92. Going to try 95 definitely, that would be the cheapest repair ever
I've a standard Japanese CDI (it's a JDM TRX).
Didn't think about fuel. Hmm. My previous SV650 accepted everything that burnt with no problem.
Still worth a try.
The thing now is that from 2k-3.5k it pulls really good. Than dies 3.5-4k. Than pulls even better.
FactoryPro kit didn't work at all. So now temporary put in old jets and needles, waiting for new Yamaha parts. I guess, the best decision is to put everything in stock and than start the investigation from the very beginning.
Still many thanks.
I'm running 92. Going to try 95 definitely, that would be the cheapest repair ever
I've a standard Japanese CDI (it's a JDM TRX).
Didn't think about fuel. Hmm. My previous SV650 accepted everything that burnt with no problem.
Still worth a try.
The thing now is that from 2k-3.5k it pulls really good. Than dies 3.5-4k. Than pulls even better.
FactoryPro kit didn't work at all. So now temporary put in old jets and needles, waiting for new Yamaha parts. I guess, the best decision is to put everything in stock and than start the investigation from the very beginning.
Still many thanks.
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Capau
- TRX-Enthusiast
- Posts: 24
- Joined: Sat Jan 28, 2017 10:11 am
- Location: Russia
Re: One more top end rebuild
Ok, after all ended up with:
1. Replacing all seals in both carbs (http://litetek.co/Carb_Kit_Yamaha_TRX850.html) aftermarket
2. Replacing input boots (TourMax aftermarket)
3. Replacing needles and tubes (OEM Yamaha)
There is still a slight flat spot around 4000rpm. At all other conditions it runs well.
Still have a question about fuel consumption, didn't do enough km's.
I'm thinking about giving Factory pro parts another chance but definitely later.
1. Replacing all seals in both carbs (http://litetek.co/Carb_Kit_Yamaha_TRX850.html) aftermarket
2. Replacing input boots (TourMax aftermarket)
3. Replacing needles and tubes (OEM Yamaha)
There is still a slight flat spot around 4000rpm. At all other conditions it runs well.
Still have a question about fuel consumption, didn't do enough km's.
I'm thinking about giving Factory pro parts another chance but definitely later.
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rednikmarto
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- Location: Plovdiv, Bulgaria. (Eastern Europe)
Re: One more top end rebuild
Hi Capau,
Do you have photos of old valves you just removed from engine ? (just curious to see what wearing developed)
Did you had compression test after the rebuild ? (also just curious about real data from this engine/head)
About your 4000 rpm flat spot - wish I could help but its little away of my knowledge/experience.
Did you tried different needle clip positions as now you have again your stock needle jet/jet needle ? (You are also now on with stock main fuel jet, aren't you ?)
Cheers,
Martin.
Do you have photos of old valves you just removed from engine ? (just curious to see what wearing developed)
Did you had compression test after the rebuild ? (also just curious about real data from this engine/head)
About your 4000 rpm flat spot - wish I could help but its little away of my knowledge/experience.
Did you tried different needle clip positions as now you have again your stock needle jet/jet needle ? (You are also now on with stock main fuel jet, aren't you ?)
Cheers,
Martin.
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cobbadiggabuddyblooo
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- Location: Brisbane,Australia
Re: One more top end rebuild
Is it 4000rpm at 1/8th, 1/4, 1/2 , 3/4 or Wide Open Throttle???
Or transitioning from 1/4 to WOT etc....
Or transitioning from 1/4 to WOT etc....
laughter is the best medicine
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Capau
- TRX-Enthusiast
- Posts: 24
- Joined: Sat Jan 28, 2017 10:11 am
- Location: Russia
Re: One more top end rebuild
It's a flat spot at any throttle position. And I think the trouble is still there. Fuel consumption is 9l/100km (180km to reserve). And I'm really fu#ked with the bike.
Thanks all guys, maybe try to sell it, or sell as parts. I got enough.
Thanks all guys, maybe try to sell it, or sell as parts. I got enough.
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Capau
- TRX-Enthusiast
- Posts: 24
- Joined: Sat Jan 28, 2017 10:11 am
- Location: Russia
Re: One more top end rebuild
Update.
Swaped CDI from another(well running bike). Still got a problem.
Did compression test. 11.5 on both cylinders exactly.
Checked resistance:
coils - in spec
pulse generator - in spec
plug caps - 9 on one and 10.5 on another. Is it a problem?
Tried to run without filterbox - runs well, pulls hard. Plugs became very light tan color. The way they should be.
Put airbox without the element - problem came back.
Now waiting for a friend on another TRX to start swaping part by part.
Bought half bottle of gas to burn the thing if it won't work.
Swaped CDI from another(well running bike). Still got a problem.
Did compression test. 11.5 on both cylinders exactly.
Checked resistance:
coils - in spec
pulse generator - in spec
plug caps - 9 on one and 10.5 on another. Is it a problem?
Tried to run without filterbox - runs well, pulls hard. Plugs became very light tan color. The way they should be.
Put airbox without the element - problem came back.
Now waiting for a friend on another TRX to start swaping part by part.
Bought half bottle of gas to burn the thing if it won't work.