Rock

So I am helping a friend, a better mechanic than me for sure, install a Factory Pro jet kit on my "98 Hawk, #1.7 RK, and he says, oh I forgot the Hawk has coolant running through the carbs. (around) Apparently it is a common thing to heat fuel to aid emissions on many motors. News to me.
I search here and didnt find any mention, should I leave it alone ? or bypass it with a new piece of heater rated hose ? There all a little cold blooded, but I am never in that big of a hurry, I always thought cool fuel was a plus...
thanks for the advice.

Slim

It's more work to bypass the system for little/no gain than it is to just leave it alone.

smokinjoe73

If you look at the schematic of the cooling system, simply clamping the hoses off will prevent the coolant from flowing to the carbs AND cause more coolant to flow through the rest of the system. I have had mine clamped for years & ride down to about 17 degrees F with no problems. Still warms up at the same rate as before but seems to run cooler in traffic. Seems to be the appendix of the bike (like the pair system). If you remove it you can go on living.

divingindaytona

Years ago bike with carbs experienced something called carb icing. They would be choppy and abrupt. This was because the carbs were cold. This is why the rad fluid is running to the carbs.

I dont see a reason to bypass this system.

Rock

Thanks for the replies, I may do it for the because I can reason if nothing else. or not. I will be installing my brand new high dollar APE cct's this weekend, so I will be there anyway.(almost) I do like the thought of coolant just cooling engine.. fuel just burning, not heating before burning idea. I guess if it is easy okay. I already have the needed parts.

RK1

I've read that when the engine is cold the warming coolant is sent to the carbs. When the engine is fully warmed up that flow is shut off. Can't find anything about that in the service manual, but my bike runs fine when it's warmed up and don't see any reason to bypass the carbs.

Rock

thanks, I like the sound of your explanation, and it makes the decision easy.

Hawkrider

Years ago when I was initially tuning the VTR I installed a valve in the coolant supply line to the carbs. Did dyno runs back to back with valve on and off. I actually lost about .5 hp with the valve shut. How? I have no idea but it was conclusive enough for me to put on a new hose and leave the system alone.

Rock

That is as solid of a reason as I need for just leaving it alone, I have new 1/4 heater hose, so I will replace the older stuff. One of my trackdays this year had the air temp @ 115 degrees, the Hawk never overheated or did the fan come on, so I see no need for re-routing coolant. It is nice to know not all things need to be re-worked.

skokievtr

Smokinjoe73, do you still stand by your above statements?

First, I did an extensive forum search on this topic (see attached).

Second, and to explain, I am currently completely disassembling and cleaning four sets of VTR1000F carburetors. In two of the four sets that I bought used which were from VTRs of questionable maintenance history, I discovered that the "Y-fittings" (see attached photos and look up “Carburetor Water Heat Joint Set PN 16026-MBB-640” $14.73 each, two required total) that the coolant lines connect were badly clogged with "gunk". I have not yet torn down the other two sets of carbs that I have alternately run on my +100,000 mile VTR that I personally have maintained, including routine vinegar flushing the cooling system and running a distilled water / extended coolant mix, vacuum draining and filling with a U-View Airlift (Airlift? Kit | Cooling | UView).

So I'm very interested in determining if the "Y-fittings" on "my" two sets of carbs are relatively clean or not.

Third, I am trying not to question the need for the VTR carb heating system or whether it works even when the motorcycle is new and/or the cooling system is absolutely meticulously maintained, that IMO based on my recent discoveries must include removal of the carburetors and cleaning of their “Y-fittings” and coolant lines.

I am more than a bit incredulous that the system in question really helps significantly if at all (and may “hurt”) during cold start-up given the “fact” that the carb coolant lines are fed from the thermostat housing before the thermostat, and thus receive cold coolant at start-up exactly when the fuel needs warming the most for better atomization; i.e., they only receive warm/hot coolant once the engine is warm.

Which leaves the theory that the system was intended be effective during high ambient humidity (i.e., with substrate temperatures being within 5 degrees F of the dew point).

This latter theory may hold merit but seems redundant given that the carbs also must absorb a very significant amount of heat via conduction and convection from and within the engines “V” which is hidden and masked from external laminar air flow by the fairing, radiators, frame and airbox.

What I am definitely questioning is the system’s effectiveness on 98% of the VTRs operating with more than 5,000 miles on them.
If you look closely at the design of the carburetors and the detachable “Y-fittings” you will see the Y-fittings have two O-rings on the spigot that plugs into the “socket” in the carb bodies (I’ll call this Spigot 1) located on one side and near the bottom of the venturi tube below the throttle butterfly valves just above where the venturi tube plugs into the rubber isolators that attach to the cylinder heads. The carb sockets are on the “interior” of the engine V and face each other. The corresponding carb body sockets are shallow in depth with a beveled bottom but do not connect coolant passageways as one would think. The Y-fittings have a brass sleeve pressed inside Spigot 1; the two - fitting spigots (call them Spigots 2 and 3) receive the coolant “in-out” hoses. Based on my examinations to date, the brass fitting inside Spigot 1 is meant to act as a flow restrictor and one-way check valve between Spigots 2 and 3. I’m seriously considering buying two new Y-fittings (Joint Sets) because the O-rings on them deteriorate (I found one presumably damaged during insertion, possibly at the factory) not so much to obtain new O-rings (Gasket Set PN 16040-MBB-640 $4.86 per pair, 2 sets required total) but to try to determine how the function when new.

Regardless, even based on the Y-fittings flowing as designed when new, the fact that they transfer hot and cold ethylene glycol (“coolant”) to the carb body via conduction across a very small exterior annular surface area that is insulated (isolated) by two O-rings and that the coolant flows through less than 2.5 mm I.D. brass orifice that is restricted into a “dead-end” socket with an effective bottom surface area 7 mm in diameter, I cannot see these system components effect being significant (though the Honda engineers presumably somehow took measurements to verify functionality).

But again my point is that on a VTR that has several thousand miles and on average at best two year old ethylene glycol coolant (hopefully mixed properly using distilled water), it is very difficult for even an expert mechanic to ensure “design flow” if not ANY flow through the Y-fittings let alone clean them adequately. I know, as I’ve run them in an ultrasonic cleaner using a solution of 5% acetic acid and a citrus-based cleaning surfactant and tried to scrape the annular space around the hollow brass insert with a small sewing needle and fine wire. I could not remove the brass insert either. So the only way to achieve near “design flow” is by routine replacement of the Y-fitting. And how many users are going to do that?

Bottom line, I may restore my system to OEM, or I may just not install the Y-fittings and connect one hose between the thermostat body outlet and water pump body inlet and see what happens…

Excuse me if the above dissertation is confusing and/or contains typos, as it's late and I wanted to finish and go have dinner.

Just_Nick

https://www.google.com/patents/US4086893
https://scholar.google.com/scholar?h...uretor+coolant

Plenty of scientific articles on the subject, if you're interested. Certainly better than guesses or assumptions.

NZSpokes

I will take the .5 hp thanks.

kenmoore

A long time ago when I first started mucking around with the carbs and an electric water pump I by passed the coolant hoses to the carbs only to reintroduce them after riding the bike. It didn't feel right so they have been on ever since.

CrankenFine

Skokie I can only say I share your puzzlement as to how these can possibly impact performance. I also noticed virtually no flow possible thru the y fittings but left the lines connected out of sheer laziness.

skokievtr

Please reread what I stated in the thread AND the attachment, which is a conglomeration of all forum threads on the subject along with other pertinent technical links.

Bottom line, I'm not questioning the usefulness of heating large carbs but I am incredulous of the theory's application execution on our VTRs, especially once mileage piles up and the difficulty to clean and verify the system's functionality.

Again, if you read my attachment, Greg N. (Hawkrider) has responded similarly several times but in his original and more lengthy response he indicated that the dyno runs were made on different dynos on different days after various modification and the discrepancy of .5 or eve 1 HP was within the margin of error rather than a reduction due to abatement of the system. Others have also subjectively and objectively qualified no appreciable change with a bypass. Those that have (see below) have not done so scientifically more of a seat of the pants, again after completing maintenance, modifications and repairs, which can skew interpretation.

I am an engineer with extensive experience in fluid and temperature dynamics and heat energy transfer, and the system on the VTR is unsustainable once it leaves the factory laboratory.

Are you sure what you felt was not instead effects caused by all the modifications you made if not also other variables? Particularly with the carbs and cooling system revisions you completed, which must have entailed mucking with the electrical system. The changes you made could very well be the source of the variance given your probable lack of incremental and scientific procedures measured back and forth against a verifiable baseline consequently makes me question the veracity if you claim.

Even with the system fully functional as designed and executed, its functionality is limited to a very narrow operating and environmental spectrum, and as I said originally, can actually hinder rapid cold start-up. Bypassing the system has not hindered smokinjoe73, and he rides as often as he can at both temperature and climate extremes!

Just_Nick

I personally don't use generalization fallacies and assumptions to justify something I do, which is why I linked pertinent data on the overall subject rather than make assumptions based on a few posts from a forum. If you want to find out on a more technical level, you're going to need to do objective testing or read what is posted in technical studies. You should know this.

NZSpokes

This is not the first time I have heard "they just run better with them on". Hawk has said this before as well.

I cant prove my ground Mod makes more HP but the bike starts and runs better for it.

Now im settled on my jet settings I will refit it and see. The worst it can do is make no difference at all.

kenmoore

I don't profess to have any discipline in engineering, thermo sciences or the like, however my very experienced butt dyno tells me that the bike runs smoother with them connected.

I can assure you that my cooling system is in first class order and I have never experienced any crud in the hoses or junctions that I have inspected every time that I have pulled the carbs(I have records and to date that has been 19 times)

I realise that the original post was not about the usefulness or effectiveness, however as this is a forum that is intended to aid fellow owners of the VTR I feel compelled to advise that my bike ran Shithouse with them by passed.

Granted, those of us that have OCMD have different setups and different riding conditions that could skew the effect of of by passing the hoses to the carbs.


In my case they are staying after having had them removed.

I trust hawk and several other posters on here.

I removed mine a long time ago and remember that the bike felt flat, I had sync'ed the carbs, done the idle drop and the mixtures both before and after only to have a bike that felt flat when bypassed.


That's as scientific as I get, and they are staying.

Could be something to do with the fact that my bike is a long way from standard.

I would be interested to find out how many people have taken them off, only to refit them ?

I am puzzled, someone with more technical ability than myself and my butt dyno may be able to help us all.

No offence intended in my post, I am now very curious !

skokievtr

NZ, see my questions / comment in red

Do you mean you currently have the carb heating hoses "bypassed" and will reconnect the system and check subjectively how the engine starts and runs and then bypass again and compare? I urge you to try cleaning the fittings (again I used an ultrasonic cleaner and different solutions of 5% acetic acid and "Oxy-Clean" and Ammonia and Oxy-Clean with limited positive results) and check O-ring condition. I also drained, filled and ran the cooling system with a 4:1 distilled water to 5% acetic acid solution, and then drained, flushed and ran it until the T-stat opened again with only distilled water, then flushed again and vacuum evacuated and re-filled with 50/50 coolant and distilled water. I also micro-filtered my old coolant and it was surprisingly free of particulates but is the breakdown of lubricant and corrosion inhibitor package as well as contaminate that "kill" coolants.

NZSpokes

Im talking about 8541Hawk whom has said this.

No Im just going to reconnect it. Not going to overthink it.

With the earth mod I went old skool and cut then soldered a new earth to the battery.

kenmoore

N.Z,

Can you post a pic next time you are working near your earth power mod.

I'm about to do some stick coils and want to do this mod at the same time.

Not chasing more power, just want to do it!

skokievtr

Jim Dougherty and Smokinjoe73 who I trust and respect did the bypass and have had no issues since, so I think I will too!

What did you do with do with the other end of the ground wires you cut that run in the harness, did you splice in and run them to ground? And as I also asked, did you do this for both the ICU and converter unit?

Hangfly