Bigger Oil Lines

A modification to increase the Oil line Size on after market Filter Relocation Kits!

Article By Tony Anzalone

2002V-Star 1100 Custom

Larry Marino & Joe Conway

provided Wording, All Information & Pictures taken from a VStar Forum Thred

Thred #

I replaced the oil lines that came with my remote oil filter kit. I put in place of the 1/8 ID oil lines that came with the kit, 3/8 ID oil lines. I felt the bigger lines would offer increased and better flow to and from the filter. Here's a couple of comparo shots.

Click on image to see larger Picture


The fittings were 1/4 pipe thread. Part numbers from

Here are pics of each item off the jpcycles site fittings... 40-0523 line 3ft 3/8.... 7200300 magnum clamp connectors.... 45-176

Click on image to see larger Picture


Look closely at the one and you'll see I put on a finned filter protector/cooloer. Found it on the Road Star site

Cant hurt and protects the filter. I opted to cut the hose clamp as in the article so that it is not seen.

Joe Conway

Hey Joe:

Those fittings are actually NPT (National Pipe Thread) sized pipe not SAE. The thread actually looks like 1/4" SAE but the closest approximation would be 5/16"-24 in SAE, but of course one would not thread into the other.

The ME remote kit uses 2 - 1/8" NPT to AN Compression fittings on the engine side, and two threaded 1/8" NPT ports on the filter side to accept the threaded end of the two connector hoses.

The reason that I drilled all four of my 1/8" NPT x 3/8" straight hose fittings out to about 7/32" to allow for increased oil flow. The 7/32" enlargement would represent a cross section profile that is about 206% of the smaller 1/8" nominal size. The actual reduction in "drag" on the flow will actually see a slightly greater improvement then the 206% would imply due to the lower frictional drag on a fluid as the conduit size increases.

The fittings can probably be enlarged to a full 1/4" ID, however, I did not want to weaken the fittings as they take the brunt of the vibration stress in a system of this type. As a comparison, 1/8" NPT PIPE, actually has an ID of about 1/4" (very odd). It is the fittings that are used with the pipe that approach the nominal 1/8".

Larry Marino

To do a Performance Increase Modification on your existing remote oil filter, here is a list if parts from the J&P catalog. There are other sources, but I’m not planning on spending the time to track them down.

To upgrade to 1/4" lines and fittings:

7400150 - 1/4" x 3’ natural/silver color SS braded hose . . .$12.95

13-350 - 1/4" Russell Tube-seal Hose ends (6 pack). . .$23.99

40-0526 - 1/8” NPT x 1/4" Straight Hose (need 4) @ . . .$2.99

To upgrade to 5/16" lines and fittings:

7400151 - 5/16” x 3’ natural/silver color SS braded hose . . .$13.99

13-351 - 5/16" Russell Tube-seal Hose ends (6 pack) . . .$23.99

40-0525 - 1/8” NPT x 5/16" Straight Hose (need 4) @ . . .$2.99

To upgrade to 3/8" lines and fittings:

096607 - 3/8” x 3’ natural/silver color SS braded hose . . . $14.99

13-352 - 3/8" Russell Tube-seal Hose ends (6 pack) . . .$23.99

40-0523 - 1/8” NPT x 3/8" Straight Hose (need 4) @ . . .$3.99

Note: All hose and connector part numbers are for Generic SS Braded hose. I listed them here to give you a price comparison when you track these items down at your local Auto supply house. It’s the SAME stuff! Now if you want to upgrade further to Sterling Chromite lines and connectors, you notice that it is more expensive. All of the connectors are also available locally in BRASS not chrome at half the cost.

All four connectors MUST be drilled out to 7/32”. It’s an easy job but they need to be held in a bench vice when you drill.

Use pipe dope or Teflon tape when you thread them in, and do not over-tighten. They just need to go in snug to the depth of the old fittings.

Let me repeat once again for the record, this post is my opinion only and the modifications to my motorcycle are my personal choice. This is not an attempt to induce or persuade anyone to perform this same modification. This information is for entertainment and informational purposes only. I will in no way warrantee the performance of this type of modification on any other motorcycle.

Larry Marino

From a Vtar board discussion between Larry M & Tony O

1st response:

Tony O: Since you and the Baron are Yamaha STAR experts (in my opinion), what is your take on the oil line size issue that seems to be an issue for many potential buyers?

I understand (from others) that the internal oil gally are somewhere around 3/8" (although that seems hard to believe since everything else on the bike is metric, lol!) Then the external lines are 1/8" so this would seem like a restriction to good flow.

However, I see it as oil INTO the filter = oil OUT of the if you restrict the flow IN then the flow OUT is really not are just slowing down the filtration process, the same amount of oil is still available to the working parts of the engine. This may potentially be a good thing.

Bigger lines would increase the rate of filtration, but not the actual volume available for use by the engine (If you put a big line in and a small line out, I can see some trouble happening! Of course this all depends on the flow directions which I am unfamiliar with.

Anyway, DADDO has written very eloquently on the subject, but (sorry DADDO, no offense meant) I don't know if he is an expert on engines, Yamaha's in particular...his theoretical information sounds correct, but what is the real life practical side? I've been thinking this over and over and just can't come to a good understanding. Any Yamaha engineers out there?

Oh yeah, we need engineers not opinioneers (some Dilbert type engineer told me that once!)

Please hel;p me to better understand before I putrchase any kit. I may just make my own which will have a completely different system (think dry sump...for HIGH revs!)

Ride safe, Larry

2nd response:

Tony O: Thank you for your response. You posed several questions regarding the various sizes of oil galleries inside the engine.

All I can respond to here is that what I have been using as a base for my data is simply the empirical evidence of what I can physically observe and measure. In addition, based upon the scale mechanical drawings provided in the Yamaha service manual, the galleries that lead to and from the stock filter chamber appear to be of a uniform size up to the point where the bearing supply gallery starts to branch and get smaller. These reductions occur at the points where the Crankshaft supply splits off. And then again at the point where the remaining oil supply is distributed through a banjo bolt to the two cylinder heads to lubricate the two camshafts and their four related rocker arms and bearing points. None of the galleries that I can observe, measure or research are as small as the 1/8” supply lines provided on most of these remote filter units, with the sole exception of the final supply conduits to the heads, starting at the banjo bolt. But anyone would have to acknowledge that this is the point in that supply system that is downstream of the point where the oil hungry Crankshaft and the large ends of the Connecting Rods take their share of the lubricating oil.

You are absolutely correct when you say: “Until someone can provide the exact engineering specifications from Yamaha it is strictly speculation one way or the other.”

This is an issue which is foundational in my argument here. None of the manufacturers of these remote filters know any more about the lubrication requirements of this engine then I do. With that understanding in mind, why in the world would they select a supply and return line size of these remote filters, that is physically smaller then anything that they can observe in this engine? Again, I am not considering the TWO 1/8” lines that supply oil to the heads, as they are at the end of that supply line.

If you are going to make an uninformed “best guess” choice here (and that is exactly what Jardine did, followed by everyone else), why in the hell would a rational person choose something smaller then what they can actually observe as the designer’s choice? With a system so critical to the protection of the bearings in this engine is it not better to make a choice that some might consider over-engineered?

Let’s say that I’m wrong here. I am completely delusional about how smaller lines will have a negative long term damage effect on the bearings in this engine. What are the implications? Some owners may be upset. A lot of others will upgrade those hoses to a larger and less restrictive size (like we do with air cleaners, and exhaust systems, etc..), and a lot of manufacturers will still want me to die or just go away. But on the other hand, what if these manufacturer’s have taken the cheap and easy way out here? I think that about everyone on the forum has at least some awareness that literally NO flow testing was done. What if that choice of smaller 1/8” lines is the equivalent of giving those engines arterial sclerosis?

You are crystal clear in your statement that no manufacturer will offer the aftermarket guarantee that I have suggested. I knew that before I offered it in my post. When a V-Star owner buys an accessory for their motorcycle, they have a right to buy that part with the reasonable expectation that it has been designed and tested to perform well and not have the potential to damage their machine. The whole issue here is that the several manufacturers that are producing these filters cannot guarantee that there will not be any long term damage simply because they just don’t know!

Now we (the manufacturer’s and I) will never come to agreement on who has made the mistake here. As far as I am concerned, the issue is on the table and V-Star owners are free to do with it as they will. There are easy solutions to upgrading and replacing the smaller lines. For those who are comfortable with those small lines on their bikes. . . well that is fine too. I wish them well.

This whole issue has taken up much too large a piece of my time already, but it needed to be said and brought into the open. Now for the most part, the arguments are all there on the forum for anyone to read and consider. At this point I will most likely just provide specific references to threads that answer specific questions. I have no particular argument with you specifically or your business and I will continue to be a regular customer.

Ride safe, Larry

Have Fun & Ride Safe

Tony Anzalone

Give the Glory to GOD

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