Vaccum Issue

[maplehawk]

Noticed that I had poor throttle response especially when cold. Bike hesitates when accelerating.

Thought issue could be synch so I checked synch. All carbs were pretty much the same, however I noticed that the vaccum was 12KPa. Manual spec gives 37KPa. Could this be my problem? If so what could cause this.

 

Bike is stock 07 with 7030 mile

 

Thx

[V7Goose]

Noticed that I had poor throttle response especially when cold. Bike hesitates when accelerating.

Thought issue could be synch so I checked synch. All carbs were pretty much the same, however I noticed that the vaccum was 12KPa. Manual spec gives 37KPa. Could this be my problem? If so what could cause this.

 

Bike is stock 07 with 7030 mile

 

Thx

Well, I don't speak "KPa" 'cause I'm just a goofy 'merican, but KPa sounds more like a PRESSURE measurement than a vacuum measurement to me. I'm not looking at the manual right now, but I DID just go out and take a look at my vacuum gauges, just for you. I can tell you from experience syncing a lot of RSVs that they generally run around 12" Hg at 1,000 RPM. Anything outside of 10-13" at idle would be cause for alarm to me. I have heard stories about the timing chain being off a notch, but never have seen one myself that had a problem.

 

When reading Yamahaha's manual, ALWAYS try to double check any numbers, either by going to another source, finding it in a different place in the same manual, or using a calculator to convert from a different measurement (such as mm HG to inches HG); I have found many of their numbers are wrong, either missing or misplaced decimals or just stupid typos.

Goose

[Eck]

Kilopascal (kPa) .....Defined as pressure of 0.0102 kg / sq. cm

 

Kilogram (kg) One thousand grams.

 

kilopascal;

A pascal is a pressure of one newton per square metre; this unit is inconveniently small for many purposes, and the kilopascal (kPa) of 1,000 newtons per square metre is more commonly used in engineering work. (For comparison, one pound per square inch equals 6.895 kPa.)

[maplehawk]

I used my synch tool before which is in cm Hg and the readings were in the mid range around 25 cm Hg. 12 Kpa is around 9 cm Hg which would not even register on my Guage (Starts at 10). So between the last synch and this check I have lost about 16 cm Hg which is about 21 KPa

[GeorgeS]

Might want to run some Sea-Foam, before you assume anything else is wrong.

 

Might be some moisture in gas, Use some HEET.

 

Or, it might be time for a new set of plugs.

[maplehawk]

Just had the 8000 mile service completed, plugs, even fuel filter, this issue has been going on for about 500 miles. numerous tanks of gas and gas cleaner have been used but problem still persists. Outside of idle under normal use it runs fine. Issues only evident on low throttle, or down changing if the throttle is blipped between down changes. After about 1- 1/2 hrs problem is less noticeable, but is still there. My service tech picked up the issues. He was a Yamaha dealer lead mechanic but now has his own buisness and cannot perform warranty work

 

Thx

[KiteSquid]

37 kPa = 10.9261 InHg = 27.75228 CmHg

 

12 kPa = 3.543599 InHg = 9.00074 CmHg

[maplehawk]

hey Kite

 

Thanks for the accurate conversions, now if you can tell me what is causing my issue that would be great:thumbsup2:

[BuddyRich]

Check your idle speed. Maybe too low. Seems mine is around 900.

[maplehawk]

spec calls for 950-1050. Mine is set in the middle at 1000.

 

This is great guys, keep the ideas flowing maybe someone will hit the solution:clap2:

[2WHEELSFORME]

After having my filters off for cleaning I experienced less than perfect running. Would not hold steady RPM was the main symptom. I found that upon reinstallation of said filters I had pinched/crimped a rubber hose coming off the top of the engine and going down thru a clip on the back of the filter housing. Got it back in the correct position and all was well. Check all hoses that they may have pinched or even left unattached when performing your service.

[Squeeze]

I don't know if there are different Issues, but for checking the Vacuum, make sure you have enough Slack in the Throttle Cable. If there's no Slack, the Butterfly Valves can be slightly open all the Time and therefore reduce the the Vacuum Readings.

 

Next could be the Idle Adjustment Screw is turned more in as it should, this would open the Butterfly Valves as no Slack in the Cable.

[maplehawk]

Thanks for all the replys. This started happening at around 6000miles. way after the 4000 mile service. Which is why i don't suspect things like pinched rubber hoses etc. During the service i just had performed my tech checked most of the things that you guys are suggesting but did not find any issues. I will be taking it to the stealer for warranty work but am loathe to do so. They tend to screw things up. If I could possibly find the solution before then it would be great

[KiteSquid]

hey Kite

 

Thanks for the accurate conversions, now if you can tell me what is causing my issue that would be great:thumbsup2:

 

 

Your engine does not suck..... enough....seriously, it is not drawing enough vacuum, and there are countless issues that could cause it, but seeing that all cylinders are about the same and you are getting 1000 RPM idle that does narrow it down some.

 

Readjust the idle for the minimum spec of 950 RPM and recheck the vacuum.

 

Like stated above, check for a little slack in the throttle cable. if the butterflies can't close all the way, you will not get a good vacuum. Nothing for the engine to suck against.

 

Are all vacuum lines attached correctly? Look in the parts book and service manual for proper routing and attachments.

 

On a cold engine, check for vacuum leaks by squirting water on the intakes,'

 

If it is a California bike (XVX13TFLC), check the Evaporative emissions control system for vacuum leaks.

 

Are all four vacuum plugs installed? Properly?

 

After checking all of that, I would have to give it a full tuneup.

[BuddyRich]

Didn't the 07's have a problem with a loose head bolt ?

[KiteSquid]

That should not effect all 4 cylinders, but is is always worth looking into

[jlh3rd]

this isn't gonna solve your prob. but my 07 with 5700 miles appears to do the same thing when cold....in neutral....give it gas and it hesitates.....just a little.....if the choke is off.....in gear seems to be fine........after warming up, not as noticeable.....i haven't changed plugs, synched carbs etc.......38 to 39 mpg......just cold natured maybe?

[Neil86]

Does the vacuum rise to normal and stabilize off idle, or stays low as you bring the rpm up?

Ignition timing looks ok?

Vacuum poor even when engine cold?

[maplehawk]

thx for all your suggestions, bike was in for recall (cylinder head bolt torque), bike is currently at the steelers for diagnostics, we could not find any logical reasons or errors for the problem I am experiencing. Hopefully they will find something. If they don't at least it will be documented and I can pursue it from there.

[maplehawk]

OK, Just got the bike back from the dealers and though I would share the results with everyone.

 

I am only stating what I was told so don't shoot the messenger.

 

Bike went in on Wednesday afternoon and I was contacted on thursday stating that the problems were caused by the carbs either gummed up or some debris and they wanted authorization to pull them apart. They told me that they had contacted Yamaha and that yamaha would cover 2.6hrs of the labor as a good will gesture and that i would be responsible for the other 1.4 hrs. Obviiously I told them to proceed.

 

They contacted me today and said that the bike was ready. They stated that

1. The idle jets/orifices were partially blocked/gummed up.
   
2. The fuel did not appear to have gone bad
   
3. That i should use 80+ octane
   
4. If bike was to be idle for more than 2 weeks that I should use Sta Bil
   
5. That they did not recommend the use of Sea Foam for the bike
   

I was a little concerned over some of these statements so I contacted Yamaha customer service and they backed up what the dealer told me.

 

The bike is running great again so i checked the Carb Synch to give me a base line and at 950 rpm I had a vaccum reading of 32 KPa

 

Hope this helps someone else down the road thanks for all of you help and suggestions

 

/Pete:thumbsup2: