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Getting both cylinders balanced after porting

Here is a question for anyone who thinks they may have the answer. How do you balance both cylinders as far as fuel to air mixture goes? Now this question has some layers to it and I will give you my symptoms. Performance overall is good, good throttle response and power, easier starts but I want to improve on each cylinder. They are not balanced, they front cylinder warm up much faster than the rear cylinder.( I checked with ana infrared thermometer) front cylinder is about 15 to 20 degrees hotter during warm up than the rear. Also the rear cylinder produces a little bit of black smoke and the front cylinder does not. Plug reading indicates that the front cylinder is perfect, nice chocolate brown plugs and the rear cylinder is Rich and has black sooty plugs. Which side of the intake manifold needs more porting to help balance the cylinders. At a loss now. Thanks/ Mitchell



You could have Sticky Valve Syndrome, SVS for short. A known Roadstar issue especially on the 04-05 models.
Yamaha sells Yamalube additive, "ring free fuel additive" which should tell you something. $40 is real pricey. Seafoam will do the job much cheaper. A heavy dose of Seafoam (8 ounces) in a tank of gas run at Highway speeds and reving it out a time or two followed buy a immediate oil oil change is the standard fix.It will smoke like it's broke. DON"T SKIP THE OIL CHANGE.
Here's how to check for the problem.

Thanks I will try it. Probably be a while since the weather is crappy now. I do however have fresh oil in the bike now. Only have run about 300 miles since the oil change. Would I still need to change the oil after the seafoam treatment?

My bike does not sound like the one in the video, mine is definitely running on both cylinders all the time. If the seafoam treatment treatment doesn't work what then?

Yes, you will need to change the oil. Run the test anyway. If that's not it, run a compression test and a leak down test.
What pipes and aircleaner are you running? Has the carb been rejetted?

Carb has been re jetted, stock headers with cobra slip on and drilled out baffles and a universal k&n air filter

When did the problem first occur? Other probables can include, valves not adjusted properly, weak coil or faulty plug wire on the rear cylinder, a slight vacuum leak on the front cylinder and even a restriction causing an imbalance between the pipes. The carb feeds both cylinders so unless the main jet has somehow been misaligned or the needle bent and the flow pattern is spraying more fuel to the rear cylinder it should supply the correct amount of fuel to each cylinder.

They bike runs good. It only has 22000 on it. After I put the k&n on and re jetted the carb I noticed the front cylinder warmed up faster than the rear cylinder. After I ported the intake manifold I was able the get the warm up temps from a cold start a little better but they still were about 15-20 degrees different. I haven't shot the cylinders after a ride to see if each one was closer in temperature I am just trying to optimize both cylinders. That isn't to say that the needle or the main jet doesn't need to be replaced it certainly could. I should examine that. Also my mileage is decent around 34 city and low 40 highway. I am going to clean the carb and check the needle and main jet, do a sea foam treatment. I may just be chasing a ghost in search of perfect performance out of each cylinder. Granted nothing is perfect. But if one cylinder is rich and one is right on, which side of the intake manifold would you open up a little more to lean out the rich cylinder? The more I have pondered this the more confused I have become. It would be easier to solve with dual carbs. Really appreciate your time and help. Glad someone is here to pass on their thoughts. Thanks

You do realise that there may just be the question that you seem to be neglecting here - What is the Compression like between the 2 cylinders ? Have you performed a Compression Test on Both Cylinders as yet ?
IF Not then it would be a good place to start with ok .... IF you have done a compression test then can you give me the figures of each cylinder in PSI please .....
IF there is any more than a 5% difference between the cylinders then you may need to look further and do another test - a Squirt of clean engine oil into each cylinder and re-do the compression test - if there is an increase in either or both cylinders then you may need to remove the cylinder heads & the cylinders - do some accurate measurements of the bore/s and pistons - wear inspection - if you are lucky everything will be within tolerance/s (specifications) and the cylinders may just need a light hone and New set of rings installed in both cyls ... From there Do a Valve and valve seat inspection and a spring length/tension test - check the valves and valve guides for wear and replace any that are not within manuf' specs and get the valves and seats cut and do a valve gring and lap them in - with good fuel tight seals for all valves ... Once done with a Top End freshen up mechanically - THEN go ahead with your modifying your fuel intake manifold or what ever you are trying to achieve 'balancing' your intake ???
It is NO GOOD even trying to acertain trying to fix a problem that does not exist - 'porting' a fuel manifold will do very little unless an uneven fit to the intake port itself is what is trying to be achieved for a better fuel air flow from carb to valve/s .... Unless you are trying to make a plenum out of the intake manifold then very little will be achieved -
The AMOUNT of fuel air mixture that goes into each cylinder is Not Determined on the intake manifold - it may be extremely minor in it's role - the amount of 'Suction' caused by the downward thrust/draught of the piston sucking or drawing IN of a Certain amount of air/fuel mix is determined by this action and trying to balance out an intake manifold is futile ...
Until you can ascertain the state of the engine's condition there is little point in doing anything regarding the intake manifold - carby jetting - air filter mods etc etc ....
If ONE cylinder is down in compression you will have a hard time in balancing anything out as far as its running condition is concerned as it will be futile .... IF your engine is showing signs of wear then do a top end rebuild and your bike will love you for it ....
It is No Good trying to treat the Symptoms - You have to Treat the Cause - OK ....
I hope this helps in your understanding of what you are asking/doing and What NEEDS to be Done Before you can even contemplate trying to go into nitty gritties of balancing ports - no good chasing your tail is there ?
Take care - Ride Safe .....

Wow! Spectacular, you are vastly knowledgeable. I am going to have to look up bunch of stuff and borrow some tools. Gosh I hope I don't need to out rings in the top end. Hopefully all I need will be a valve adjustment.
Thanks you all for such fantastic news info

Good on ya Mitch - There are a lot of variables involved and quite a few considerations to take into account - but if you are chasing an issue like you are describing then a compression test should be done first before anything else - do a dry one first and then one after a squirt of oil in the cylinders (through the plug hole ...) It will reveal if the compression is good bad or otherwise and the oil one should reveal whether or not it is cylinder rings or the valves not seating properly - Do some reading up on the subject and see if you can either buy or borrow a compression tester & a shop manual - fairly cheap for the benefit they can be and a really handy tool to have in your toolchest.

Let me know the results if you can - a small discrepancy is ok - but always check the Service Manual of the bike for the proper specifications as every bike is different although similar ....
Good luck with it all - one thing about the V twin engine is that there are only 2 cylinders and they are usually very accessable for doing top end work and rebuilds - Don't be put off if the bike needs a set of rings and a valve grind, once done then it will run sweet as .... maple syrup on a pancake .....
Cheers from an old ex mechanic biker in OZ .... (I will try to help as best I can from here) - Research is the Key ok.

Research is brother in law is a fantastic mechanic and may have a compression tester. It's going to be some time before I will be able to report any results. Definitely need to get a hold of a service manual. Thanks so much again for your time. Financial position puts me at a loss for parts right now but research and testing should be able to happen here in the near future. Not afraid to turn wrenches, had to just to get by with everything! If I can rebuild diesel truck engines I can do this. Knowledge is power and I thank you for yours, now I have a much better direction to follow.
Keep it rubber down

Cheers Mitch - you are on the right track now - i'm sure between your brother in law and yourself you will be able to determine the best plan of attack .... You should be able to download a shop manual for it off the net ... - 449 pages of it ok covering the 1600cc and free of course - in PDF format - easy download - I just saved one for my own files for future reference if needed.
Reference pages Section 3 page 18, 19 & 20 Compression testing - OK Listed as 3 - 18, 3 - 19, 3 - 20 .....
Cheers and Ride Safe ok ...
Greg - frostbite


Thanks this manual will be very helpful

I consider myself mechanically inclined but entry level. I read over the manual, very informative, but lapping or grinding the valves seems beyond my capabilities, adjusting them may be within my grasp. As a diesel mechanic I have left that kind of work to the pros( it's just faster to get rebuilt heads and slam em out so to speak.) I haven't been that involved in any motor. Replacing parts is one thing. Never messed around with the valve train. Caterpillar engines are easy to rebuild when you just slam new parts in and torque down. Any advice. Manual seems to be a little vague. Anyone know an approximate cost of getting the valve train inspected and adjusted? My roady has 22000 miles and to my knowledge has not anything but regular oil changes.

Hi MItch - I have been busy with the repainting of my bike and not been here for a week or so, otherwise I would have replied sooner - I haven't looked in the manual for valve inspection and adjustment as yet but give me a couple of days and I will see what is entailed and get back to you ok ... Most of the bikes I have worked on have been reasonably easy to check and adjust the valve clearances be they Screw adjust tappets or Shims - the trickiest ones are the Desmodromic Valves on the Ducati's - Mechanical Opening & Closing are a real bitch to do ... the majority are fairly easily done.... I will have a look and see what the GO is and let you know how best to tackle it ok .... I think some of the late Jap Bikes have Hydraulic tappets similar to the HD's - The VN900 I have has Shims and theya are fairly easy to do - No special tools needed, just a set of feeler gauges and a small magnet for lifting the shims out with - I bought a Hot Cams set of shims for $150 - good investment because most shops will hit you up $12 to $15 bucks for an exchange shim ....
I'll get back to you in a couple of days Mitch OK -
Cheers & Ride Safe -
Greg (frostbite) ....

I have a bore scope and peeked at the cylinders and they are carboned up I am guessing that the valve are the same. Going to adjust the valves then run a compression test. And when it's ready to run I am going to do a seafoam treatment. Run another compression test and take another peek in the cylinders. It appears that the only adjustment you can do is between the two valves on each rocker, hydraulic lifters control actual lash.. looking like I should double check my adjustment with a dial indicates before I go any further.... Roadstar clinic has some good threads on the subject.

Got the top end torn down now and doing a top end refresh, scrubbed the carbon off the heads and out of the ports, lapped the valves, lots of carbon build up and enough on the valve seats to prevent any benefit from adjustment. Plus had a 30 lb increase on cylinder 2 when I did a wet compression test. Now I am just waiting for enough money to get the gaskets, piston rings, and valve seals. I the meantime I have been detailing the cylinders by polishing the cooling fins. Leak tested the valve after lapping with water, no leaks after twenty minutes. Will leak test again after I put the head back together with air through the ports and watch for bubbles. Just glad the weather hasn't been any good around here. If it was I would really be itching to get it back together.

Great stuff Mitch - good to see you are on track for getting it sorted OK ... Smiley-laughing
Cheers Mate - Ride Safe ....

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