Reanimating a greybike RVF400 (NC35)

[Krooklyn]

I should have taken a bit more time to write. Sorry for the kinda-sorta drive-by.

I've heard from the grapevine that the NC is sensitive to its valve gap in terms of making the most power, especially when hammering the valves up around the 16k (HRC CDI) redline. The spec is the spec and there's nothing wrong with keeping it in spec if you're not chasing horses, but my attitude is while-you're-in-there etc. You're definitely not going to get stranded. But I might pull away from you down the front straight at Thill

The HRC CDI only revs to 15.5K. Even so, for you to rev that high and not have long-term issues you'd have to do some major mods (valve springs, cams, etc) to see any real benefit. From someone who's actually done a number of these adjustments, I can say that for my setup (YMMV) I noticed a seat-of-the-pants dyno difference (bike seemed a little more restricted is the only way to describe it) when I went from the HRC valve clearance specs to the street clearance specs and plan to put mine at the top of the street specs when I do them shortly.

 

[RVFRick]

Guys, I don't have an HRC CDI as far as I know so my redline is 14.5k.
What are the HRC valve clearances?
When you do a valve inspection do you find that you need to adjust much or do they stay mostly the same?
Can I assume gaps will almost always trend toward smaller from valve seat wear (no carbon build up if bike is properly tuned)?
Put another way, for the life of your bike will I need ever thinner shims each valve adjustment?

 

[thenewwazoo]

The HRC CDI only revs to 15.5K.

Not sure what to say to that except “no it doesn’t”. My HRC-equipped bike will happily rev to 16,5, which is as far as I’ve ever wanted to push it, and I’m confident the (MC19) tach is accurate.

I don’t know about long term valve clearance patterns, unfortunately. Maybe Krooklyn does. The big V4s get tighter over time, not looser, but that’s not worth much.

 

[Krooklyn]

Not sure what to say to that except “no it doesn’t”. My HRC-equipped bike will happily rev to 16,5, which is as far as I’ve ever wanted to push it, and I’m confident the (MC19) tach is accurate.

I don’t know about long term valve clearance patterns, unfortunately. Maybe Krooklyn does. The big V4s get tighter over time, not looser, but that’s not worth much.

I've heard of fake HRC CDI's revving to 16.5K, but I've read that the actual HRC CDI only increases the rev limit by 1K. Maybe the Interwebs are wrong?

 

[Krooklyn]

Guys, I don't have an HRC CDI as far as I know so my redline is 14.5k.
What are the HRC valve clearances?

IN - .20 EX - .30

When you do a valve inspection do you find that you need to adjust much or do they stay mostly the same?

I always mean to right this down and will look to see if my last check has it written somewhere.

Can I assume gaps will almost always trend toward smaller from valve seat wear (no carbon build up if bike is properly tuned)?
Put another way, for the life of your bike will I need ever thinner shims each valve adjustment?

Depends - you may need to move shims around, so always good to keep the old ones in case you can re-use them on a different valve later on.

 

[RVFRick]

IN - .20 EX - .30

Sorry, gotta ask, are these max numbers or revised means?

Standard
IN .12-.18 (0.15 mean)
OUT .21-.27 (0.24 mean)

 

[Krooklyn]

Sorry, gotta ask, are these max numbers or revised means?

Standard
IN 0.12-0.18 (0.15 mean)
OUT .021-0.27 (0.24 mean)

Revised means.

 

[RVFRick]

STOCK
IN .12-.18 (.15 mean)
OUT .21-.27 (.24 mean)

HRC
IN .17-.23 (.20 mean)
OUT .27-.33 (.30 mean)

Works out to a delta of +.05IN and +.06EX. Both healthy increases and, oddly, not the same.

Someone please educate me. Bigger gap means the valves will stay closed for a longer duration and not open as far, right? How does this help/affect performance? Further, does it make sense to do this on an otherwise stock setup?

When folks talk about HRC this and that is it an all or nothing set of mods you're supposed to make like cams, petcock vacuum delete, bigger jets, airbox, exhaust, sparkplugs, etc.?

I get that HRC bits are geared toward higher performance and track riding but is it worth it or just mostly bragging rights?

 

[Kestrel]

To my understanding... and this can also be used to help understand camshaft duration...

Valves that are too tight result in more lift on the valves from the cam... This keeps the valve open longer. That is good at high RPMs because it translates into more air in the cylinder... But the downside is that at low RPMs, some of that intake charge gets pushed back out and is lost due to exhaust and intake valve overlap. At high RPMs, there isn't enough time for that to happen per given intake charge, so you get a little more air in there.

If the clearances are on the loose side you get better filling of the cylinder at lower RPMs, thus more torque in the lower end.

Camshafts that have a lot of lift / duration thus run shitty at idle, but were made for serious performance on the high end, which really explains a lot of the old 60s/70s V8 muscle cars that barely loped along at idle, but screamed on top...

Somebody correct me if I'm wrong here. This is my super hazy understanding of the matter.

I can first hand tell you that when my little Ninja 250 valves were tight, performance was better at high RPMs, but it was even more gutless down low. After a valve adjustment where I put everything at max loose prior to my 8k around-the-USA trip this past summer, I absolutely gained back a shit ton of low end.

 

[auntiebling]

as an engine warms up, clearances typically close aka get tighter. the bigger danger with clearances on the Tight side, is that valves never completely close and a valve gets "burnt" as hot gasses slip past it.

if it gets really bad, the engine won't start because you don't develop enough compression. this scenario is very real on single cylinder engines, probably less likely the more cylinders you have as the others might not be as bad an the engine will start on those.

once an engine is spinning, the idea of Compression Ratio changes a little, as things are happening so quickly the air/gas mix doesn't have time to escape out a slightly open valve, but can light off and make a kind of cutting torch through that little opening.

if you aren't chasing horsepower, i think it was already mentioned, setting valves on the loose side is the safe approach for engine longevity.

 

[Krooklyn]

STOCK
IN .12-.18 (.15 mean)
OUT .21-.27 (.24 mean)

HRC
IN .17-.23 (.20 mean)
OUT .27-.33 (.30 mean)

Works out to a delta of +.05IN and +.06EX. Both healthy increases and, oddly, not the same.

Someone please educate me. Bigger gap means the valves will stay closed for a longer duration and not open as far, right? How does this help/affect performance? Further, does it make sense to do this on an otherwise stock setup?

When folks talk about HRC this and that is it an all or nothing set of mods you're supposed to make like cams, petcock vacuum delete, bigger jets, airbox, exhaust, sparkplugs, etc.?

I get that HRC bits are geared toward higher performance and track riding but is it worth it or just mostly bragging rights?

The HRC setup for the NC35 doesn't have different cams. It's pretty tame actually; you take some transmission bits from the NC30, some jetting changes to the carbs, put on a bigger airbox (with a scoop), raise the rear end, fab an oil cooler from other Honda models and that's pretty much it. On one of my prior bikes (RC51) that had aftermarket cams (Moriwaki) and JE pistons the valve clearances were same as stock, so I have no idea why the HRC specs would be looser on the NC35.

 

[RVFRick]

Bike culture in Taiwan

Okay, not a project update but I thought I'd share anyways. Just returned from a quick trip to Taiwan. Jessica and I accompanied Mom to help her settle some personal affairs. It was a welcome break from work which has been keeping us busy. It's always exciting to Taiwan as I enjoy observinf the scooter culture there where every red light intersection is a treat. Every green light is like a Moto GP start. Cheap entertainment! Rain or shine, hot or cold (it was cold and wet our entire trip) people ride. Men, women, old, young. Never saw an incident or close call everyone rides their ride and cagers are typically mellow. No one uses their horn. Saw some cool Japanese custom bikes, a cool BMW covered scooter, a few unexpected hogs, some rare Arai helmets, and a resourceful cardboard recycler

 

[Slow Goat]

That’s nice and all but.....get to work on that bike!


Cool pics.

 

[RVFRick]

Session 23: Last two carb diaphragms

Had some free time today and went to the bat cave to tidy up the tools. It got rather disorganized over the past months as I've been working on a bunch of projects at my mother's rentals like replacing furnaces, water heater and faucets, fence mending, repairing a garage door opener, window blinds, etc. It's never-ending. It's hard to find time for the RVF.

Anyways, I had some free time today to square away the tool chests. It felt good to get personal time. Organizing tools into their labelled drawers helped me track what I have on hand. I was happy to locate my missing RVF spark plug wrench. And I also uncovered a bag of allen wrenches. I now have maybe 5 full sets of inch allen drivers. Not so useful. Oh and I have 3 feeler gauges for some unknown reason!

Once the work space was tidy and swept, I revisited the carb assembly which have been beckoning for attention since June of last year. The last time I touched them I removed the float bowls and two of the diaphragm covers. To be honest, the complexity of the carbs still baffles and intimidates me because I don't fully understand all the parts and how they function.

I removed the remaining two diaphragm covers. Fingers crossed the rubbers would be in decent shape like the first pair as I haven't found spares anywhere online.

Three phillips panhead screws hold the black cover in place. Why are they black and not silver like everything else? They feel and sound metallic but maybe they're glass filled plastic. I carefully cracked the screws careful not to strip out the soft metal using my $3 Daiso (JIS?) phillips driver set. Who knew JIS screws can be identified by the dot on the head?

JIS (Japanese Industrial Standard) differs from Phillips. Phillips are designed to cam out! Get your geek on here http://www.instructables.com/id/When-a-Phillips-is-not-a-Phillips/.

With the screws out the cap came off easily and I felt a spring pushing force. A 5" long compression spring pushed against the cover presses the needle slider in place.

I gingerly teased the "O-ring" portion of the diaphragm seated in its carb die-casting groove. It came out of its gland groove easily without sticking too much. Luckily it appeared supple and hole-free and without compression set. There was minor cracking of the O-ring portion. For the most part it looked good enough to reuse with the help of a little RTV.

The slider part didn't come out so easily. I tugged on it with some needle nose but it was a little stubborn. Pulling harder it slipped out. Varnish from the old gas made it stick and hard to pull out. I'll have to be sure to clean these parts really good so parts can move freely.

More carb disassembly to follow.

 

[GB500guy]

Hi Rick, this place in the UK sells many carb parts including diaphragms for many models. You ship them the slides and they install new diaphragms. For the RVF400 their web site says "call" for availability. I ordered new Japanese-made float valves and seats from them for the CB-1; they also list them for the NC35:

http://www.nrp-carbs.co.uk/index.htm

And this place is another option for carb O-rings and seals. They are in Thailand but the parts have a good reputation on the CB-1 forum:

http://litetek.co/ReplacementPartsHonda.html

This place, also in the UK, has some unique parts for the FVR/RVF bikes as well:

https://gfracinguk.com/?sesid=mrkctdv7kg618b3u2il9k6ttg0

-Bill

 

[RVFRick]

Thanks, Bill. I got the carb kit from Litek a while back. I will keep NRP and GF as backups for other parts. My choke cable (an NLA part) might need replacing as one of the plastic adjustment knobs is cracked.

 

[Whammy]

Did you get that helmet???
I’d of had a hard time walking away from it if it was for sale.

 

[RVFRick]

It's was a sweet helmet not sold in the US - Limited edition of 500 signature of Honda Kazuo development leader of RC30 and serial number printed on the back. Check out the cool IOM TT model.

To sweeten the deal the shop keeper discounted it to $700. Online some sellers are gouging at $1k. Though tempted, I couldn't justify another helmet. In fact I had just bought a plain white one in the US a week before the trip. My other excuse is he only had a medium and my melon takes a large

 

[Whammy]

It's was a sweet helmet not sold in the US - Limited edition of 500 signature of Honda Kazuo development leader of RC30 and serial number printed on the back. Check out the cool IOM TT model.

To sweeten the deal the shop keeper discounted it to $700. Online some sellers are gouging at $1k. Though tempted, I couldn't justify another helmet. In fact I had just bought a plain white one in the US a week before the trip. My other excuse is he only had a medium and my melon takes a large

Ohh that's not a good one. Arai helmets Med/Large are the same shell, only difference is the inside face pads if I'm not mistaken?
Imagine how bad ass it would be wearing that on your maiden ride?
You can easily sell the white one on teh barf.

 

[RVFRick]

LOL! Actually, I misspoke, thinking back I did try the V4 helmet on and the guy said it was too loose on my noggin to be safe so it musta been an XL.

Anyways, my white one was too good a deal to pass on. Used, clean, cherry condition, camera mount (plan to get a GoPro. Suggestions?), tinted outer visor (like it so far) and a quick release buckle (hate it).

Can buy a ton of stickers with the $ I saved