Poor MPG and top end performance.

[Pasta Burner]

I’ve been thinking my gas mileage is poor but with lots going on bike wise and other I haven’t put too much thought into it, after-all riding is my hobby and putting food into its belly is part of the game.  But I finally had some time to calculate and keep track and I’m only getting about 85 miles to the tank before the warning light flashes. After I filled up yesterday I went for a little ride and dumped 3/4 can of sea foam in the tank when I got home.

On another note some of you may remember I just installed progressive springs this season and that has me much more comfortable riding the bike and pushing her harder (the old wet noodles made me uneasy especially when the forks would bottom out between shifts).  What I noticed during my ride it would pull nice till about 5k then not necessarily bog down but just stop pulling and struggle to get past 6k and eventually just wouldn’t rev any higher.  Maybe that’s normal…maybe not.

thoughts on both issues or either appreciated.

[luvmy40]

Definitely not normal!

The Gen 1's will pull hard to and past red line(no rev limiter). I've had my '83 over the ton many times. She did not get great mileage, 34-36 mpg on the best days, but I really rode her like I stole her more often than not.

My '86 is almost as fast but not as quick, if that makes sense. She gets closer to 40 mpg, but I also didn't tend to push the red line as hard on her.

You should be able to cruise at 65 mph, drop a gear or 2, go WOT and hold on for dear life.

Edited August 23, 2021 by luvmy40

[Pasta Burner]

So where’s a good place to start diagnosing?  This isn’t the first seafoam I’ve put in but for sure the strongest concentration.  I do know all four are firing using an infrared on the exhaust.
 

plugs? Carb sync? Carb clean other than the seafoam?

good to know I should be expecting better performance.

[cimmer]

First place I would check is the carbs, starting with the diaphragms and checking for holes in them. They will wear and developed pin holes in them that effect the performance of the bike.  There are replacement available for a number of source, but dont buy this ones from China that are on ebay cheap.  Here one source that has them available. https://www.siriusconinc.com/pro-detail.php?pid=&product_id=1794  Another thing to try on the carbs is called shotgunning them with carb cleaner. Check the tech library or do a search on it in the internet and you will find a procedure on how to do that. The Vmax guys come up with it I believe and it does seem to help out with carbs that have some dirt in them. Also if they are okay or need replacing, you need to also sync the carbs and see if that helps. Most likely it is off some but shouldnt effect the bike like you are describing. 

I would check plug wires and spark plug cabs and replace or upgrade them if needed, and yes the spark plugs also.  Becareful as there is a small o-ring that holds the sparkplug wire in the coil when you remove the wire, as you dont want to loose that.

You may also need to get the valves clearances set properly if that hasnt been done or if you are not sure when the were last done. There is a kit available from one of the members here and all he request is that you buy new valve cover gaskets from him.

I have an 89 and I usually average between 35 to 43 mpg depending on my wrist action and have no problem going up to redline quickly.

Hope this helps.

Rick F.

[skydoc_17]

Hey Guys,

You gents are spot on with your description of places to check on Tom's bike! Any engine that runs on fuel needs three things. Air, fuel and spark. Because he said it feels like it is straining to go past 5 grand, and did not suggest that the ignition just flat cuts out at 5G leads me to believe that it is an air/fuel related problem rather than an ignition problem. Closely inspect the air filter. Better yet, If you are running the paper one, just replace it. If you are running the K&N filter, clean it! I personally run the K&N filters on both my VR's and every time I clean the air filter, I replace the Fuel Filter as well. Set all 4 Idle Mixture Screws at 2 1/2 turns out, and "Fine Tune" them from there. The inspection of the Carb. Diaphragms Simmer mentioned is an excellent place to start! If the sliders are not damaged, the Diaphragms from Sirius are an excellent choice. If the sliders are damaged, then complete replacement assemblies are the way to go. I offer complete Plug Wire with NGK caps upgrades for $65 that would take care of that issue for years to come, If you are interested. A good Carb. Sync is also an excellent investment in time for these bikes. Once you have taken care of these "Basic" items, if you still have this issue Tom, then the list of things to check becomes a bit more "pricey". Keep us posted on your results.

Earl

[Pasta Burner]

Thanks all.  For syncing the carbs is there a preferred tool?  I’ve read @skydoc_17 post in the tech section and Earl uses a carbtune Mercury looking guy that I found for about $130, Amazon has a gauge style for $70.  Any reason to spend the extra few bucks?

[saddlebum]

Motion Pro uses manometer fluid and is probably the most accurate and sensitive though incorrectly used the fluid could get sucked right out of it.

Morgan Carb Tune is probably one of the more popular and since it uses rods rather than fluid, fluid loss is not an issue. Storage and transporting is not an issue either.  However on the odd occasion the rods have been known to get sticky if some foreign material found its way into the tool. I occasionally check mine by using a homemade 5 port manifold to which I connect all four hoses and a mighty vac applie vacuum and make sure all four rods read the same. You can also use this test on the gauge type to ensure they all read the same as well.

The Four Gauge set is probably the most trouble free and unlike the first two it does not need to hang vertical and can be used in any position. You do have to check the gauges and make sure all four read in sync with one another as with the morgan.

Home Made you can also make your own using four gauges or a single gauge with four valves on a rigged up manifold. Below is a PDF for one I made from scrap parts. You can make a similar one by combining brass parts as well (that is How Marcarl made his which is where I got the idea for mine ) The single gauge eliminates discrepancy between gauges and the valves allow you to both select the cylinder you want to check and dampen the pulses so you get a steady needle reading. Use of the valves to dampen pulses eliminates the need for restrictions in the hoses or the more expensive fluid dampened gauges which I find often tend to loose their fluid over time The down side is you cannot check all four cylinders at the same time you have open and close each valve one at a time and compare your readings that way. But it does make for a very compact and effective unit.

HOMEMADE CARB SYNC TOOL.pdf

Edited August 25, 2021 by saddlebum

[luvmy40]

If you go with dial gauges, get liquid damped gauges and make sure to install restrictors at the far end of the hoses.

 

I've had the Morgan Carbtune Pro for many, many years and it just works. You might need to clean the rods and channels if you get any contamination in there. It's not a dificult job.

[Pasta Burner]

Ordered the carbtune pro 4, should be here this weekend.

[Squidley]

29 minutes ago, Pasta Burner said:

Ordered the carbtune pro 4, should be here this weekend.

I've been using a Carbtune for 15 years, haven't had any issues and it's been all over the USA.

[saddlebum]

On 8/24/2021 at 5:51 PM, luvmy40 said:

If you go with dial gauges, get liquid damped gauges and make sure to install restrictors at the far end of the hoses.

 

 

With the setup I built using the adjustable valves fluid gauges and restrictors are not required. I later upgraded to a bigger gauge for the bigger face and this gauge did happen to be liquid filled. Other than slightly changing how I adjusted the valves to smooth out the needle it really did not make any difference in the overall performance of the tool.

Edited August 29, 2021 by saddlebum

[Pasta Burner]

Small update.  

What I don’t think I mentioned is that when I put the seafoam in when I got home the other day is I shook the tank up well and let it idle for 20 min or so to hopefully get it into the carbs while it sat.  
Rode her work today and I immediately noticed better idle from cold while I got my gear on, hardly any choke needed and stabilized well, once I got to the four lane she pulled till redline in first without hesitation then pulled hard till 7rpm in second and Immediately bogged down.  Had to shift anyway and third was smooth but no road left to throttle it. Went in the close to home gate to get on base and she ran great all the way to my  building.  On the way home traffic was such a drag I couldn’t even near 5k in second on I15.  But seems to be running better on seafoam alone, we’ll see what tomorrow brings.  
And my carb sync is in the mail so still excited to see what that reveals.

[cimmer]

Seafoam is my go to for all my small engines. I even mix it with the gas when I fill up my gas cans, and I always store my engines with Seafoam in the tanks and have no issues with startup at the beginning of the seasons. And yes I use it in my Venture all the time and store it with Seafoam and none ethanol gas in the tank. Seafoam is great for keeping the gas fresh also.

Not sure how much you but in the tank but on your next fill up I would dump half the can in and go drive it like you stole it. It does help to clean up the carbs when it can get thru the passages to begin with.

Rick F.

[Pasta Burner]

So this could be a big part of the issue.  I can hear hissing from somewhere, now the search is on to find it.  This tool gave me exactly where to start though.  That port is hooked to right side front carb.

Edited August 28, 2021 by Pasta Burner

[cimmer]

Are you talking about the vacuum ports on the intake runners here?

The only connection I am aware, hooks up to the vacuum port on the #2 intake runner for the front carb on the left side of the bike as you sit on it. The other 3 ports should have vacuum caps and clamps on them and really are only used with balancing the carbs. The vacuum line goes from that port up to the pressure sensor that is used for the ignition advance on the bike. It could be possible that hose has a leak in it and might be causing the poor performance and MPG.

Rick F.

[Marcarl]

9 hours ago, cimmer said:

Are you talking about the vacuum ports on the intake runners here?

The only connection I am aware, hooks up to the vacuum port on the #2 intake runner for the front carb on the left side of the bike as you sit on it. The other 3 ports should have vacuum caps and clamps on them and really are only used with balancing the carbs. The vacuum line goes from that port up to the pressure sensor that is used for the ignition advance on the bike. It could be possible that hose has a leak in it and might be causing the poor performance and MPG.

Rick F.

That vacuum line also has a restrictor in it., kind of the same things as the crab tune tool.

[Pasta Burner]

@cimmer what I was intending to show is that I had a vacuum leak on the right front carb,  using some spray I located it was the intake boot, it still needs the be sealed a little better but I was able to tighten things down enough to get a reading.  I was able to sync all four, I’ll report back once I button it up.

 

on a side note, is there a recommendation for the carb drain hoses?  Two of mine are missing/ cut way short.  My gut says they don’t need to be anything special, considering they only see fuel once in a great while…I think.

[cimmer]

They are only used when you open the float bowl drains and direct the fuel to the right and left side of the bike so you can catch the drain fuel into a container instead of having it go all over the engine. Your call if you want to replace them but they can be a pain to get to with the carbs on the bike as they are in the middle of the carb bank.

Good catch, I hadnt thought about the intake boot being loose and causing the leak. Replacement are available if you think you need to replace them. Check out https://www.siriusconinc.com/pro-detail.php?pid=&product_id=122177  but they are showing out of stock..  imagine that.. 

Rick F.

[saddlebum]

11 hours ago, cimmer said:

They are only used when you open the float bowl drains and direct the fuel to the right and left side of the bike so you can catch the drain fuel into a container instead of having it go all over the engine. Your call if you want to replace them but they can be a pain to get to with the carbs on the bike as they are in the middle of the carb bank.

Good catch, I hadnt thought about the intake boot being loose and causing the leak. Replacement are available if you think you need to replace them. Check out https://www.siriusconinc.com/pro-detail.php?pid=&product_id=122177  but they are showing out of stock..  imagine that.. 

Rick F.

That's It ? @Marcarltold me I had to attach a 40 mile plus tube to it before I open the drain and that he would take care of the other end

[Pasta Burner]

15 hours ago, cimmer said:

They are only used when you open the float bowl drains and direct the fuel to the right and left side of the bike so you can catch the drain fuel into a container instead of having it go all over the engine. Your call if you want to replace them but they can be a pain to get to with the carbs on the bike as they are in the middle of the carb bank.

Good catch, I hadnt thought about the intake boot being loose and causing the leak. Replacement are available if you think you need to replace them. Check out https://www.siriusconinc.com/pro-detail.php?pid=&product_id=122177  but they are showing out of stock..  imagine that.. 

Rick F.

There is something funky going with that boot for sure.  It’ll be a carb off investigation, when I went to tighten the inner socket head screw it was a 4.5mm rather than 5mm like the rest.

 

it performed much better today still some popping and hesitation above 6k but I think it just needs to be ridden hard, which is difficult in rush hour.  By the time I got to work it had started a high idle 1700 and I notice the throttle has about a 1/4 freeplay before it engages.  I don’t remember it being like that.

Edited August 30, 2021 by Pasta Burner