Moving the Rectifier/Regulator to a cooler spot

[V4 Rosso]

Within the first 1000km after I aquired my 3rd gen it left me stranded with a burnt RR and a battery that was whistling like a kettle with boiling water. First symptoms were the tach jumping around and random misfires of the engine. Later I noticed the seat getting uncomfortably hot (due to the boiling battery) Luckily I was just two kilometers from home but it is slightly uphill and in 30C weather and full gear it was no fun pushing the bike all the way home. The RR was not the only thing overheating.

Here is a pic of the overheated Honda RR. At least it bleeds when it dies :goofy:

I wrote a message about my misfortune on a local VFR owners messageboard and soon learned this was quite normal for a VFR. Some bikes had suffered from a burnt RR three or even four times. I hate getting stranded and soon started looking for a solution to this overheating regulator. As most had good results with adding a cpu fan on top of the RR I tried that first as I had several spare CPU fans in my parts cabinet. The new upgraded RR had cooling fins and between these fins I cut some thread so I could bolt the the fan directly on top of the RR with a nut on each bolt to act as a spacer between the RR and fan.

I was having doubts if this would work as there is not much cool air entering the area behind the right side fairing where the RR is located. So it looks to me the fan is merely moving hot air around. But that wasn't the biggest problem I soon found out, as it didn't take long before the fan broke down. I replaced the fan and the one I replaced it with worked for maybe two months before it broke down too. So it looks like these small cpu fans can't cope too well in this harsher environment. Maybe the bigger fans used in a computer power supply can take more of a beating, but there is hardly any room to put one of those behind the 3rd gen fairing. To me it looked that even when you managed to squeeze one in there, there would not be enough air volume left for it to efficiently move some air around.

When installing the third cpu fan I also added some thermo sensors to get an idea as to how hot the RR gets on an everyday ride. I used two sensors, one attached to one of the fins of the RR and one attached to the subframe very close to the RR. The sensors were wired to a digital thermometer that I put behind the clear screen of my tank bag so I could keep an eye on the temps while riding.

After firing up the engine the temp of the RR rises quickly to somewhere below 40C/100F and then continues to rise slowly with the increasing temp of the subframe. During normal riding conditions (outside temp 25C/77F) the subframe temperature gets up to around 50C/120F with a RR temp of 64C/147F but in lots of stop and go traffic the subframe temperature got up to 64C/147F and the RR to 74C/166F. At one time I recorded a RR temperture of 87C/189F(didn't have a sensor attached to the subframe at that time). So to me it was pretty clear that the RR was not able to dissipate enough heat through the subframe as that got pretty hot itself. Maybe there is even more heat transferred from the subframe to the RR than the other way around? The original RR, as shown in the first pic, can only transfer heat through the subframe unlike the upgraded RR that has fins.

When I stopped the engine but let the cpu fan running for a minute untill the temp reading on the RR dropped to about 45C/113F and then switched off the fan, the RR temperature would rise again considerably from the heat transferred from the main frame to the subframe. The left side of the subframe stays marginaly cooler, maybe 5C/10F.

Either way, even with a cpu fan the RR would still get very hot and in a further attempt to reduce heat buildup I put a cpu heatsink between the RR and mounting plate on the subframe:

Shortly followed by another heatsink attached to the inside of the subframe:

I also cut some O rings out of gasket material and put them between the mounting points of the subframe and main frame in order to reduce heat transfer between the two. But all these modifications showed absolutely no improvement in either subframe or RR temperature readings.

So it looked like I either had to cut a big hole in the fairing to increase air circulation or move the RR to another cooler spot. I choose the later option and decided to move the RR to the rear fender. Other options were move it to the front, below or next to the oil cooler, or attach it behind the licence plate. It doesn't look like there is enough room near the oil cooler and I needed the space to replace the horn for a bigger and louder version. Also it would put the connector in a dirty environment with a higher chance of corrosion of the terminals and all the problems that come with it. That also applies when you put the RR behind the license plate (behind the rear wheel on the inside of the mudgard), lots of crud builts up in that area. So I opted to put it on top of the rear fender under the seat where it stays dry and clean. The idea was to bolt it directly on top of a large passive cooler I took out of an old non functioning amplifier. The passive cooler is 160x80x28mm which is a perfect size to fit into the recess of the rear fender above the rear wheel.

First I made an outline of the RR on the fender and used a dremel to cut a hole that would fit the RR

Next I did the same for the heatsink: drill holes it the appropriate positions for cutting threads to bolt the RR to the heatsink and for holes to rivet the heatsink to the fender. I also drew the outline of the RR on top of the heatsink along which I put some sealing compound in order to get a water tight seal between the heatsink and the fender.

Here it is riveted to the rear fender.

And here is what it looks like from below:

Even at full compression the rear tire does not come anwhere near the fins of the heatsink.

Now all that is needed is to lenghten the harnas by about 0,5m.

This is how I prefer to splice two wires together: I slide the exposed ends of the two wires together and tightly wind some electric wire around the joint and then put some solder on the joint. Then I put some acid free vaseline on the soldered joint and slide some heat-shrink tubing over the it. The vaseline is to keep any moisture out.

As you can see ther is still room for the passenger grab handles to be folded under the seat.

This setup has now worked flawlessly for 4 years/45k mls and after I completed this mod I ran with a temperature sensor attached to the RR for some time and in 36C/97F degree weather the reading topped out at 44C/110F.

I think that's good enough.

RECT/REG are merely one of the electrical components of two wheel vehicles that simply perform current rectification and regulation of battery voltage. In the future, however, as the use of electrical components in control mechanisms continues to progress, RECT/REG devices will become essential for two wheel vehicles. Consequently, those devices will be required to provide even higher levels of reliablity. One of the factors that contributes to reduced reliablity is excessive internal temperature rise caused by poor heat radiation conditions. For the future, it will therefore be necessary to develop RECT/REG devices having low heat radiation dependancy and improve temperature toughness while focusing on this point.

[SEBSPEED]

Thanks for putting this up here for us! :beer:

Have you had any heat issues after lots of miles and dirt buildup on the heatsink?

[i3v4]

A most excellent post - Many Thanks - I know what I'll be doing next weekend !!!

[V4 Rosso]

Thanks!

Have you had any heat issues after lots of miles and dirt buildup on the heatsink?

No problem at all, and to my surprise there is hardly any dirt buildup on the heatsink. I expected a lot of dirt getting trapped between the fins but no. When I wash the bike I do occasionally spray some water on the heatsink, that's all.

Btw, the finned RR I used is not the original that Honda sells for the VFR, but that for a lot of smaller Hondas like CBR250/400RR & Honda Foresight scooter but also some bigger bikes like the VT750 and Pacific Coast that have a similar charging system to that of a VFR. Honda part# of the VFR RR is 31600-MV4-010, this one has part# 31600-KFG-860 and comes at half price. Manufacturer part# is SH691-12.

Here is a list of of bikes that should be able to work with the SH691-12 RR:

• Pantheon 125/150 2t(Chiocciola 125/150)
  
• Dylan 125/150
  
• SH 125/150 (XLV 150 Varadero (01/05)
  
• VT 125 Shadow (99/00)
  
• Foresight 250
  
• Jazz 250
  
• 250 Forza X/EX
  
• CBR 250/400RR
  
• VFR/RVF 400
  
• CB 500
  
• CBF 600/S
  
• CBR 600/F (91/00)
  
• CB 600 Hornet (98/05)
  
• CBR 600/FS Sport (00/01)
  
• NTV 650 Deauville (98/01)
  
• VFR 750 (90/97)
  
• VT 750 Shadow (97/03)
  
• PC 800
  
• CBR 900 RR
  
• VTR 1000F (97/00)
  
• XLV 1000 Varadero (99/00)
  
• CBR 1100 XX (96/98)
  

[teksdailyride]

wonder if this would work on a 6th gen.

[Rivcyko]

wonder if this would work on a 6th gen.

First mod I made, was just putting a fan on it. So far,......**fingers crossed**,........35,000miles,.........

[Guest]

Thanks!

Have you had any heat issues after lots of miles and dirt buildup on the heatsink?

No problem at all, and to my surprise there is hardly any dirt buildup on the heatsink. I expected a lot of dirt getting trapped between the fins but no. When I wash the bike I do occasionally spray some water on the heatsink, that's all.

Btw, the finned RR I used is not the original that Honda sells for the VFR but that of a lot of smaller Hondas like CBR250/400RR & Honda Foresight scooter but also some bigger bikes like the VT750 and Pacific coast that have asimilar charging system to that of a VFR. Honda part# of the VFR RR is 31600-MV4-010, this one has part# 31600-KFG-860 and comes at half price. Manufacturer part# is SH691-12.

Here is a list of of bikes that should be able to work with theSH691-12 RR:

• Pantheon 125/150 2t(Chiocciola 125/150
  
• Dylan 125/150
  
• SH 125/150 (XLV 150 Varadero (01/05)
  
• VT 125 Shadow (99/00)
  
• Foresight 250
  
• Jazz 250
  
• 250 Forza X/EX
  
• CBR 250/400RR
  
• VFR/RVF 400
  
• CB 500
  
• CBF 600/S
  
• CBR 600/F (91/00)
  
• CB 600 Hornet (98/05)
  
• CBR 600/FS Sport (00/01)
  
• NTV 650 Deauville (98/01)
  
• VFR 750 (90/97)
  
• VT 750 Shadow (97/03)
  
• PC 800
  
• CBR 900 RR
  
• VTR 1000F (97/00)
  
• XLV 1000 Varadero (99/00)
  
• CBR 1100 XX (96/98)
  

Top post.

Plasma.

[Dutchy]

Pity that spot is already taken by the alarm system on my bike (Spyball), I would have relocated too.

For those who are considerng doing this, look into the "VFRness" that member Tightwad sells. Ask him to lengthen the wires that go to the plug into the R/R and you donot need to splice... :biggrin:

[V4 Rosso]

wonder if this would work on a 6th gen.

The RR on the 6th gen is located near the head tube isn't it? Air circulation is a lot better so failure rates will be a lot lower than that of 3rd and 4th gen VFRs. The 5th gen RR got more cooling fins and is located to the slightly cooler left hand side of the subframe. I do hope the RR of the VFR1200F is more robust as it is quite expensive to replace at €393. At least Honda used this idea and made sure the cooling fins are exposed to the abundant flow of fresh air circulating around the rear wheel :laugh:

pic made by solomoto

[teksdailyride]

Lol u would think that it would b more reliable. But i have ended up on the short end of the stick so far. Ive hot 25k miles and im already on my third r/r and fourth stator.and ive been over everything more then once. But man o man do i love this bike. I wouldnt mind if i had to replace it twice a year ide still keep it. But for me any little helpto make it last longer is money well spent in my book.