Moving from a standard "Shunt" regulator to a MOSFET regulator
従来型の「シャント式」レギュレータからMOSFET式レギュレータへの変更

MOSFET vs. Standard: Standard regulators dump excess energy as heat, often burning themselves out. MOSFETs run much cooler and provide more stable voltage.
MOSFET vs. 従来型（シャント式）：従来型のレギュレータは、余剰電力を熱として逃がす構造のため、熱でパンク（破損）してしまうことが多々あります。 対してMOSFET式は、発熱が大幅に抑えられるだけでなく、より安定した電圧供給が可能になります。



バッテリーはほぼほぼ新品なのに、どうにもその日一発目の始動で、セルの回りが渋い。
The battery is basically brand new, but for some reason, the first start of the day feels sluggish—the starter motor just isn't turning over smoothly.

そこまで固いオイルでもない（15W-40）し、電力起因ぽい回り方。
It’s not like the oil is super thick (15W-40), and the way it’s cranking feels like an electrical issue.

色々測ってみてると、3000rpm、5000rpmと回していったときに、15.8V
ありゃー、全然兆候なかったけど、バッテリー虐めてたのかぁ。
After measuring a few things, I saw it hitting 15.8V when revving to 3,000 and 5,000 rpm. Yikes... there weren't any warning signs, but it looks like I’ve been cooking the battery.



2000円の5Pの最廉価で済ませても良かったのではあるが・・・（Sence線は無視）
I could have just settled for the cheapest 5-pin option for 2,000 yen... (and just ignored the Sense wire).

MOSFETから選択して「翌日着」「日本製」に絞ったところ。MOSFETで最廉価に仕上げるよりも、1万近く余分にかかった（涙）
But once I narrowed it down to MOSFET types that were "Made in Japan" and available for "Next-day delivery," it ended up costing me nearly 10,000 yen more than the cheapest MOSFET build would have (cries).

MOSFETは5Pだけど、自己出力から12Vを読むそうな。
The MOSFET unit is a 5-pin, but apparently, it reads the 12V from its own output.
*Sence線 (Sense Wire): Many older regulators have a brown "sense" wire to monitor battery voltage. Modern MOSFET units often do this internally (detecting voltage at the output terminal), which simplifies the wiring.



新しいほう、コネクタのロック角がメスになってる。
On the new unit, the locking tab on the connector is female.
ロックはかからずとも、車体側に嵌るだけは嵌るものの・・・ゆるゆるなんで純正コネクタに組み換え。
While it technically fits into the vehicle-side plug even without the lock engaging... it’s way too loose, so I’m swapping the terminals into the OEM connector housing.



純正と同じ取り回しには、コード長が若干不足というより、コネクタがフレームに当たって無理なので。
Trying to follow the same routing as the original part didn't quite work. It’s not just that the cable length is slightly short; the connector actually hits the frame, making it impossible.
180度ひっくりかえして、ダストカバーに切れ込み入れてコネクタ通した。
Instead, I flipped the unit 180 degrees, cut a notch into the dust cover, and threaded the connector through that way.



レギュレータ取り付けボルト...老眼で、明暗差キツい奥まったとこがほとんど見えず大苦戦
The regulator mounting bolts... man, with my aging eyes, it was a real struggle. I could barely see anything in those deep, recessed spots where the contrast between light and shadow is so harsh.



復活。　5000rpmでも14V台前半でピタっと安定。
Back in business. Even at 5,000 rpm, the voltage stays perfectly stable in the low 14V range.
しばらく様子見して怪しいようなら、虐められてたバッテリーを再チェックかな。
I’ll keep an eye on things for a while, and if anything seems off, I’ll have to re-check the battery—it definitely took a beating from that overcharging.

転載は特に問題ないです。Everything is working fine.
ご利用ください。Please feel free to use this as a reference.
配線については
車両側6P
DC入力プラス（赤）Sense（12V参照）DC入力マイナス（黒）
AC出力（灰）×３
レギュレータ側5P
DC出力プラス（赤）　　　　　　　　DC出力マイナス（黒）
AC入力（灰）×３
As for the wiring:
Vehicle Side (6-Pin):
• DC Input Positive (Red): Battery connection.
• Sense (12V Reference): Voltage monitoring line.
• DC Input Negative (Black): Ground.
• AC Output (Gray) ×3: Stator/Alternator phases.
Regulator Side (5-Pin):
• DC Output Positive (Red)
• DC Output Negative (Black)
• AC Input (Gray) ×3

をそのままつなぐだけです。
Simply connect these directly.

車両側にあるSenseはMOSFETでは使用しません。
従来型レギュレータでは5Pでも6Pでも使えますが、6Pのほうが無難ではあります。
The Sense wire on the vehicle side is not used with this MOSFET regulator. While you can use either a 5-pin or 6-pin version of a conventional (shunt) regulator, the 6-pin is generally a safer bet for those types.

This post was translated with permission from this site.  著者の許可を得て、こちらのサイトより記事を翻訳・転載しています。
You can check out his other posts here.他の投稿はこちらからチェックできます。

Hi all,
Bit slow off the mark. I’ve had Sylvia for nearly two years now and she’s a work in progress, fine tuning to suit my old lady riding style! She’s the standard green with a not standard brown seat. Slowly putting her back to her more upright style after the last owner converted her to a cafe racer. Only new to riding so she’s good for a first bike. Learning every day!
Photo is what she looked like when she came to me. I’ve gone for more upright bars, blasted and repaired the leaking tank (need to put the pin striping back on), removed the multitude of fuel filters, built a new clutch cable after the old one snapped, and refitted the little travel tool kit box.
I still need to figure out how to make her a bit quieter as there is leaking at the muffler end of the header pipes, plus there’s no heat shield. Leg gets quite hot! Looks like the pipes are not stock, or so Yamaha say so I can’t find a carbon crush gasket, plus there’s no clamps to hold things in place. But I see lots with the single muffler dual header system so maybe they were for Australian imports. On the lookout for a heat shield, but for the meantime I’m wrapping the pipes and puttying up the exhaust joins.
Happy travels!

Rebuilding the engine and the last thing we need to solve is the carb. We can't repair it and we can't buy replacement parts for it. So my question is what's an alternative carb to use?

This post is copied from the FaceBook group with a few addendums from the comments. Original post credited to Steve M.

I have had problems ranging from rough running, petrol leaking over the garage floor and cylinders that are so full of fuel that the bike does not turn over due to "hydraulic lock" all depending on how long the bike is left for. Clearly there was a problem with fuel passing through the fuel tap (petcock), even in the off position, and then past the float valves, that also should close off the supply.



First I tried a carburetor rebuild with new float needles and a good clean . Second I put a new diaphragm in the vacuum operated valve in the fuel tap (petcock). I even tried replacing the fuel pump after reading every single carburetor or fuel related comment ever made on the SRV250 forum!!! However I could not find out why the fuel issue continued.

But here is the solution. To the right hand side of the fuel tap (petcock) is an extra fuel line marked "return" which is connected to one of the carburetors. The fuel appears to go from the tank, to the fuel tap (petcock), to the vacuum operated valve, to the pump, to carburetor 1, to carburetor 2 then back to the fuel tap (petcock). Inside this return connection on the fuel tap (petcock) is a spring and a valve that while the engine is running and fuel flowing has pressure that opens the valve and allows fuel to return to the fuel tap (petcock). When the engine stops the spring closes the valve. This is similar to the vacuum operated valve on the other side of the fuel tap (petcock) in that it is designed to stop fuel leaking into the carburetors or cylinders when the engine is not running.


So many forums and workshop manuals refer to the diaphragm operated valve as being the cause of all these problems but no other bike has the complicated system that the SRV250 has in that there is an additional valve on the other side of the fuel tap (petcock). I removed it and inside it was corroded and jammed in the open position allowing fuel to drain, via gravity, from the tank into one of the carburetors bypassing all other valves designed to stop fuel leaking. A good clean of the valve seat & a new tiny oil seal on the valve has now cured the problem. Perhaps this highly unusual valve that is not mention in workshop manuals, forums etc could also be a cause of other members fuel related problems that they have not been able to resolve by normal well known methods. I know this has been a long explanation of this issue but this is a very rare return valve that nobody other than SRV250 owners have and all our bikes are now old and therefore likely to have these corroded malfunctioning valves.

Hello all,

The tank fuel filter on my Renaissa has been internally affected by corrosion and maybe beyond repair. I have tried repairing it with epoxy but some parts (connection to hoses and inner seats) have been compromised.

It seems that Yamaha do not manufacture the part anymore and none of the suppliers I have contacted has been able to provide one.

The part number is:

4DN-24560-01
Filter Assy

Another option would be to adapt a filter assy from other model but I have no idea which would be compatible with the tank... any idea?

Thanks in advance for your help!

Jorge

I'd like to demonstrate how to make a silencer for a short exhaust system on a motorcycle. This will not just reduce the volume of your pipes, but more importantly will give you the necessary back pressure to help reduce the risk of burning out your valves and what-not from running way to lean.

I'm basically just running my headers as my exhaust, so this is how I went about it.
You'll need a small diameter pipe that will fit into your exhaust.  About half the diameter and preferably made of stainless steel.  I placed the length of pipe into my header and measured where it needed to be cut.

Then I cut that and drilled holes every 3cm or so, alternating 90 degrees and offsetting by 1.5 cm. (See the pic)
Next, I drilled and tapped a hole in the header for a bolt to hold the silencer in place.


Next, I wrap the silencer with steel wool. Again, stainless is best (or even heat resistant fiber glass if you can find it) then wrap that with wire to keep it in place.  On the short front header, I needed to provide more back pressure, so I also stuffed the silencer with the much larger grain stainless steel (from a kitchen sponge type thing.)  Make sure you do that before you wrap the outside, so when you run the wire through the holes, it also secures the steel wool inside the silencer.

Now, carefully insert the silencer into the exhaust while rotating so the steel wool doesn't bunch up.  When you you get it in place, tighten the bolt to hold the silencer pipe and you should be good.  The picture below shows the placement of the silencer in the longer header pipe before the bolt was tightened.


This method provided the bike with the back pressure needed to run smoothly and also gives me the opportunity to adjust the silencer when I feel it's necessary.

If you give it a shot, I hope it works out for you as well as it did for me.

I've installed an Ace-2802-2 Digital Meter on my bike as part of its rebuild and thought I'd detail the wiring for that install.  I've seen pics of them installed on other SRV's, but could find no info online.

I've removed the original headlight, but other than that have a standard wiring harness on my 1993 4DN2.

Detail　　ー　　Bike　ー　Meter
Neutral light　ー　Sb　ー　Purple
Key Switch　ー　L　ー　Red
Ground　　ー　 B　ー　Black
L. Turn Signal　ー　Dg　ー　Orange
R. Turn Signal　ー　Ch　ー　White
Tach Signal　ー　Y/B　ー　Yellow (separate plug)
High Beam　ー　 Y　ー　Light Green

Meter Clock Power ー Brown ー run line to battery (+)

Unused Meter - Oil warning light - Grey (not available on SRV)
Unused Bike - Turn Signal (+) - Br/W
　　　　　　  Various Switch (+)? - Br

Yamaha Wire Color Code
Sb = Sky Blue
L = Blue
B = Black
Dg = Dark Green
Ch = Chocolate
Y/B = Yellow with black stripe
Y = Yellow
Br = Brown
Br/W = Brown with white stripe

So, that's pretty much it at this point.  Once you've removed your headlight and stock meter assembly you'll be left with two black connectors which will have the majority of those wires.  The turn signal wires need to be directly connected with the individual direction wires since the stock meter only gives you a general signal, not left or right.

The small connector with 3 wires (B, L, Br) is basically power.  The other connector (Br/W, Y/B, Y, Sb) is for individual warning lights.  The Sb wire really looked Grey until I stripped the wiring harness back and saw some of the un-weathered bit.

The Yellow wire for high beam warning comes from the headlight connector and there is also an additional ground that you'll want to keep installed in the harness.

I'll post some pics once I get it wheeled out of the shed.

Here it is post install:

Hi everyone. I bought this 1992 SRV last fall, rode it 20 meters into my garage, and have been re-furbing it over the winter. I'm really glad to have found this forum! Look forward to learning from your projects and sharing mine.

Bill

主要諸元 / The Specs for the SRV250 4DN are as below:
※[]内はSモデル / ※[] Figures in brackets are for the 'S' models

全長-Length / 幅-Width / 高-Height
2095 / 720 / 1055mm
[2095 / 720 / 1105mm]

シート高 / Seat Height
760mm

車軸距離 / Wheelbase
1390mm

車体重量 / Weight
144kg(乾)
[146kg(乾) ]

燃料消費率 / Gas Mileage
56.0km/L
※定地走行テスト値 / Tested on flat surface

燃料容量 / Fuel Capacity
13.0L

エンジン / Engine
空冷4サイクルOHC2気筒
Air Cooled 4-cycle Overhead Cam 2 Cylinder

総排気量 / Total Engine Displacement
248cc

最高出力 / Max. Metric Horsepower
27ps@8500rpm

最高トルク / Max. Torque
2.5kg-m/6500rpm

変速機 / Transmission
常時噛合式5速リターン / Constant Mesh 5 Speed Return

タイヤサイズ / Tire Size
前-Front 90/90-18(51S)
後-Rear 110/90-18(61S)

バッテリー / Battery
YTX7A-BS

プラグ / Spark Plug
CR7HSA

オイル容量 / Oil Capacity
全容量-Full Capacity 2.0L
交換時-On Oil Change 1.6L
フィルター交換時-When Changing Filter 1.8L

スプロケ - Sprockets
前-Front 15｜後-Rear 45

チェーン
サイズ-SIze 520｜リンク-Links 106

車体価格 Base Price

449,000円（税別）(Without Taxes)
[479,000円（税別）]