Another RVF thread!

[matty_boy]

Thanks buddy. It just so happened that I was out there last year for bike week. I had a right laugh looking at all of the Harley hogs. But I did have a good chat to quite a few blokes who had done loads of work to there bikes.

I tend to get over to Florida ever year, last year we went over in March and it was a touch on the chilly side. So we just headed down to Miami for a few days then nipped over to Paradise Island in the baharms for 5 days then back to Orlando.

I am just hopping it will be nice and sunny this year. We are heading out on the 18th of April for 2 weeks, should be staying around the Disney area for most of the stay. But I always have to get down to South beach for a few days so I think we will head down there after a week.

I cant wait, just wish I had brought more Dollars when the rates where good.

[RVFHooligan]

So it seems I'll never be completely finished with this bike. After getting the bike running fairly good last week, I went to start the bike on Sunday and it didn't want to start initially when cold. Finally got it started and it just wasn't running quite right and had a different exhaust tone. Checked things over and noticed the left front exhaust pipe was only slightly warm. Somehow dropped a cylinder, now I got a Triumph Triple! Set about to diagnosing the problem, spark is good all around but that particular cylinder the plug is fouled, dry, black soot. Got to be a problem with the carb. Now I know I have had the carbs off several times, taken them apart, cleaned them, compressed air in all the lines, adjusted, etc. Ah fuk, I can strip the tank and carbs off the bike in 10-15 minutes now, I'm a pro at it. Upon increasingly closer inspection of the carb(s) I find on that carb that the spring loaded tip of the float needle valve is seized up. With some carb cleaner and a tiny sewing needle and a little prodding I eventually free it up and clean it out. OK, so I check the rest of them and they are all fine, rubber tips are intact and normal, clean out the holes for the valves, re-assemble. OK, might as well check the float levels again since the stuck pin surely altered the settings on that carb. For some odd reason it appears all the float levels are slightly higher than normal, 1-2 mm, and I followed the instructions in the Haynes manual perfectly. Anyway, slightly higher float levels (floats sit LOWER in the bowls) cause a leaner carb, hence the reason for my richer pilot screw settings. Soooooo, got it all re-assembled and all is well, however I need to re-balance the carbs again to re-check. I have a mate who works at a motorcycle shop and he is going to "borrow" their new $500 Digital Carb Balancer this weekend. So we'll see what the high tech equipment says vs. the old carb tubes. Hopefully, this is the final bit of tuning. And I ordered a fresh set of plugs from a distributor in the US. I've cleaned the fouled plug but I can;t be sure it's 100% and I want to eliminate all variables. Going for 100% on this re-build so I want to be absolutely sure. Till next time.....

[CMSMJ1]

Keep it coming mate. You need to get it finished and get some pics for us to see how it stands after all this work!

[RVFHooligan]

OK, after many sleepless nights and banging my head against the wall trying to sort the fueling I have come to the conclusion that it might be something else. Maybe BIG mistake #2 on my part with this rebuild. Not checking the compression or pulling the heads when I had the motor out of the bike. I have had the carbs off and apart over a dozen times and can never find anything wrong with them. My current theory is low compression due to poor valve sealing. Therefore low vacuum pressure pulling on the carbs resulting in weak fueling. If I pull on the choke and essentially "dump" fuel into the intake ports it revs like a champ, but with the choke closed it runs flat like it is lean. So you may recall I increased the pilot screw settings which richened it up and it ran better but then I was fouling the plugs. I am getting dry carbon fouled plugs which I have read may be caused by "fuel mixture too rich" and/or "compression loss due to imperfect cylinder-piston seal or valve seating". The reason I am leaning towards the latter is because when I used the carbtune I mentioned how the Mercury was barely getting sucked up the tubes 1-2 inches on the throttle and didn't even enter the tubes at idle. I assumed small high revving motor with less vacuum but this may be wrong. So question to all who have used a carbtune, how high up the sticks did your Mercury rise? I obviously need to check the compression and today I plan on buying or borrowing a compression tester and check the numbers. Remember, this bike sat for YEARS without being run or properly stored, with flash rust in the tank, so maybe some corrosion worked its way down to the valves and they are not sealing properly. Worst case scenario if this is true, I'll pull the heads and do a proper valve job. I have OEM Honda head gaskets and rocker gaskets already so I'm somewhat prepared. I think I can pull the heads off with the motor in the frame, just have to remove rads, exhaust, etc. Anyone done this? How difficult? Any tips on valve jobs? Does this all seem to make sense? Because I was beginning to lose my mind fiddling with the carbs. It's just such a pain in the ass because (most) everything went so well on this rebuild and I can start the bike and ride it around the neighborhood and everything else mechanically works 100% and looks fantastic, it just runs like a bag of crap no matter what I try to change or adjust. ARgh!!!!!!

And I have checked spark all around and it's good and even installed a brand new set of plugs. Also set pilot screws back to stock settings. I have removed and checked the choke plungers several times also, so it's not a faulty choke. Air filter is brand new so it's not a blocked filter. Here's how crazy it is, with no choke, stock pilot settings, I get a cold downpipe on # 4 cylinder no matter what, with motor cold or hot. The bike will run and start but #4 is dropped. With choke on or partially on #4 picks up and I get a hot downpipe but then #2 gets dropped probably from a fouled plug running with the choke partially on. So I am thinking the vaccum in #4 is so weak it can't even suck the fuel through the pilot jet/slow idle circuit and the needles and main jets don't come in to play until 1/2 to full throttle. Using the choke pumps fuel into the cylinder below the butterfly and it runs then but you obviously can't run on the choke. Hopefully this eventually makes sense otherwise I am going to chop the bike to bits and I'll send each of you a piece! LOL

Also, when I checked the valve clearances they were all within spec, actually more on the tighter side of the range. Would the clearances be tighter if the valves weren't seating fully?

#1 Intake - .127, .152 Exhaust - .229, .254
#2 Intake - .127, .127 Exhaust - .254, .229
#3 Intake - .152, .127 Exhaust - .254, .254
#4 Intake - .127, .152 Exhaust - .229, .229

[RVFHooligan]

Fuk.

I'm an idiot. I should've went with my gut instincts all along. I've made 2 big mistakes on this rebuild. 1) Trying to save the original paint on the tank and not strip it properly and deal with the flash rust problem. 2) Not rebuilding or at the very least checking the top end of the motor when I had it out sitting on the ground for several months. Again, all seemed well initially so I didn't want to pull apart an original, low mileage (8200km) HONDA V4 motor, which are "supposed" to be bullet proof motors. I drained the coolant initially and it was clear and clean. Drained and inspected the oil twice and it didn't show any signs of wear. The bike started and ran, although not 100%. I assumed it just needed a little refreshing and tuning. Pulled the rocker covers, clean as a whistle. Valve clearances within tolerance. Everything seemed OK, or so I thought. So where am I going with this?

Cold engine compression test results from last evening: ALL 4 cylinders exactly the same, after repeated tests............................100 psi.

Now all the books and manuals I have read state 100 psi is the cutoff point for a dead motor. Although the motor was cold, I seriously doubt if the motor was warm that the numbers would have been much higher. Confirms my suspicions. Anyway, I did one "wet" compression test on the #1 cylinder and it jumped up to 165 psi. Not good, indicates poor piston-bore sealing. I didn't even bother checking the other cylinders. I may do it later but I am already facing the reality of a top end rebuild.

I can only assume that this poor bike sat neglected in Japan for years with either water in the tank and cylinders or exposed to the elements. I doubt it went in the water completely (ie:submerged) because all the electrics are fine and that would have been a quick and easy fix. What are the odds of all 4 cylinders sustaining exactly the same amount of damage resulting in the exact same low compression numbers? Again, it would have had to be something that directly affecting all cylinders at the same time and same way. Anyway, I need a drink right about now.

[matty_boy]

Gutted for you mate. But i would think that a rebore and over size pistons would fix the issue.

You never know you might get lucky and the rings are just worn. Fingers crossed it wont be to bad.

Matty.

[RVFHooligan]

Ah hell, I'm not 100% convinced at this point. I've been thinking, and the motor was stone cold, temps were in the 40's and 50's over the weekend. The bike was not recently run, so most of the oil was probably drained into the pan and not in the cylinders. The last I ran it I was fiddling with the choke to get that #4 cylinder to fire, I might have flooded the cylinders, washing down the walls, removing the oil. C'mon, work with me here guys. It seems inconceivable that all 4 cylinders would have the EXACT same problem. There was no difference between any of them. The battery might have been a little flat at the time so it might not have been cranking at full strength and not reaching peak compression. Also, when the bike was running it was never smoking bad either, It just doesn't add up. It just doesn't seem right. I dunno. Maybe I'm in denial. I'm going to get some Yamaha Combustion Chamber Cleaner first and let that sit a few days, it removes carbon build up on pistons, rings, valves, etc. The rings might be stuck, the valves might not be closing because of build up, etc. For $20 I'll try that, why not at this point, then change the oil, put the carbs back on, get the bike running up to full temperature, and perform a more thorough and accurate compression test. I should try this first before I hang myself, right?

I'm also going to buy a stronger carb cleaner solution and actually soak the carbs. I think I have even heard of a carb agitator? I have used spray carb cleaner about a dozen times with compressed air, but maybe there is still a small passageway that is clogged. Doubt it, but again, at this point, why the hell not.

[alexibrow]

What are the odds of all 4 cylinders sustaining exactly the same amount of damage resulting in the exact same low compression numbers?

It's a bit odd, as it goes. Is there any sign of oil smoke from the exhaust? If not, then I wouldn't immediately fear the worst, as it's unusual to lose compression due to a poor piston ring seal without some blow-by as well.

Is the compression tester you've used getting a good seal on the cylinder head?
o Is the o-ring in good condition?
o Are the spark plug seats clean and free from pits/corrosion?

If the seal looks good, borrow a second compression tester and confirm the readings you got from the first tests; if that's not practical, use the compression tester you have on a known good engine and compare the readings you get with the engine manufacturer's specs.

If the compression tester is found to be good, take the rocker covers off, spin the engine over by hand and check that the valves open and close without sticking, and return to the fully closed position (although you may already have confirmed this by checking the valve clearances). BTW, the clearances would be greater than standard if the valves were sticking open, assuming that the clearances had been set with the valves operating correctly. If the clearances had been set once they were sticking, they could appear to be correct!

Lastly; is there any other way that all cylinders could be down on compression, other than valves or pistons clearances? Maybe the cylinder heads aren't properly sealed for some reason? How easy would it be to check the cylinder head bolts' torque settings?

EDIT - just saw you've posted while I was writing this! Chin up, I think you're right; it's very unlikely that the readings you've taken are correct.

Here's a thought: check for air leaks on the inlet side; eg vacuum pipes, breather hoses, the little rubber caps sealing the vacuum take-offs on the heads (I assume the 400 has these, as my 750 has them). An easy way to check for leaks is to run the engine at a constant rpm, then judiciously spray some Easy-start or WD-40 (or similarly combustible fluid) on the inlet side of the cylinders (but not near the air filter intakes); any air leaks will suck in the spray and you'll briefly notice a pick-up in rpm. Air leaks will definitely cause the symptoms you describe, and with a bike that's been standing for a while could be a sign of perished breathers etc.

Good luck, I'm sure you'll get her sorted soon. I'm keeping my fingers and toes crossed for you mate! :D

[Cammo]

It just doesn't seem right.

I'm with you on that.

I only reckon that because the engines are tough units.

One nc30 I have (with only 12k km's on it) was sitting for years. After thoroughly cleaning and inspecting carbs and electrics, replacing all fluids etc, it fired up like it hade never been laid up.

Persevere, I reckon it might all turn out ok!

[CMSMJ1]

Shit Jeff... this sucks. I reckon if it comes to a top end stip and fettle then 6 months down the line you won't regret it as then the entire chassis and the top of the motor has been in your eye and felt the attention it needs. The bike will be better for it.

The motor won't be dead..it is sleeping

I agree with the guys about eliminating "user error" from the compression test...not that I am saying you are useless mate...but just because!

good luck with it man..25 pages of kickass RVF build might just scrape up to 35 or 40 pages at this rate.

The easy fix is to send the motor to socal and the G-Force gang for some 57mm pistons on a fresh rebore and a sneaky look at 70+ bhp....