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70hp orifice change

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mikegonzo721

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Part #28 states, When changing orifice plugs all plugs must be changed to orifice plug #33. Just wondering why? I'm in the middle of going through all the carbs and was ordering my kits when I saw this statement in the parts list.
Thanks
 
Yeah, I see it too and there's no information out there to explain this. The description included "rstr", which I assume stands for "restrictor". But that's just a guess. I know most new motors have computer controlled idle RPM's, and they're much lower than most of us set our old motors at. Is the EPA trying to limit how much smoke and fumes our old 2-strokes produce?? I have no idea what that text is all about. I can find lots of places that are selling the #33 orifice plug, but I'd be tempted to re-use the part I took out. The only thing I can think of is that the parts is somehow sealed into place and when you remove it, the replacement part comes with some type of adhesive on the threads.
 
Thanks for the info. I found the RSTR a bit strange too and looking on line found a possible clue as to what it stands for as well. Restrictor was what I came up with. I've cleaned these carbs a few times now and the results slowly get better. I thought the new jets might be the ticket.
My issue is a sudden rpm drop after running WOT for less than a minute. She screams at 5100 rpm 30 mph but then suddenly bogs to half rpm. I place the controller in neutral then idle for just a bit and then hammer down and we get 5100 rpm for less than a minute and the half rpm. I would really like to figure this out it's a bit frustrating.
Some background ... I replace all 3 coils the rectifier new head gasket poppets and springs , thermostat. New exhaust gaskets and power head to adapter plate gasket, new starter and solenoid and new fuel pump. With this latest carb cleaning, I'm replacing all carb gaskets and needle valves and seats. Along with all gas lines and adding an inline filter (10 micron). I think if all that doesn't cure my WOT loss of power then I think I'll be chasing a vacuum leak.
Any thoughts?
 
Sound like it dropping a cylinder/s...hook a timing light up and mointer it when it fails. Most likely a pack failing
 
Is there a bench test that would be accurate knowing my issue is at high rpm? It starts just fine with the auto choke and just a few pumps of the cold motor idle lever at the controller. I did forget to mention the link and sync is perfect, by the book.
 
Pumping the fast idle lever is a waste of effort.-----It does nothing.------Push key in and hold it in while cranking it over for cold starting.
 
racerone said:
Pumping the fast idle lever is a waste of effort.-----It does nothing.------Push key in and hold it in while cranking it over for cold starting.
Click to expand...
Racerone, Sorry let me clarify the fast idle pump. I do it after the motor has started. Kind of like reving the engine in a hot rod! Just knocking the cobwebs out!!! Do you know of a bench test that will diagnose a high rpm short in the power pack? Or am I hanging off the transom with a timing light like fastbullet suggests?
 
You do not have to hang off the transom at all !----You lay the timing light on a seat.------Observe the flash of the light when engine falters.-----Nothing to it.
 
Oldsaltydog said:
Do you have a functioning overheat alarm? Sounds like an oveheating situation. When was the waterpump or impeller last replaced?
Click to expand...
The alarm works and yes I replaced the water pump this last June. While on the muffs I'm able to keep a hand on the exhaust plate, Its hot just not hot enough to burn you. I know that's not very technical but I don't have an infrared thermometer. Again both poppets, springs and thermostat were replaced last month. Here are my symptoms again, The motor starts easily, auto choke works perfectly. While underway mid range I have a little shutter or vibration and at full throttle 5100 RPMs it will run perfectly and like a light switch it drops RPM's after about 15/20 seconds to 2500 to 3000. After backing off to neutral I can repeat this problem over and over again. While cleaning the carbs this last time (not finished yet) I found something stuck in one of the low idle jets. Probably a piece of fuel line. I've replaced everything from tank to carbs and added an inline filter.
 
I haven't tried that but after my fuel delivery overhaul. I'll give it a go. New hoses plus a filter and a carb cleaning, new float seat and needle. Adjust float drop and level. And the typical cleaning. Granted this will be the 3rd cleaning in 3 trips less that 2 hours a piece.
 
Ok back from the lake! New fuel lines and inline fuel filter along with a quick carb cleaning made an improvement on my sudden drop in RPMs from WOT. But....still had the issue. Just not quite as bad. I did the timing light check on each plug wire to rule out a power pack problem my results were inconclusive. I'm not sure what I am looking for besides the obvious no flash from the timing light. I thought I saw a miss in one of the cylinders but I could not reproduce it.
The next thing I did was pump the bulb while WOT and I didn't have an rpm drop. I disconnected the tank line and pumped the bulb and it got hard as a rock on the first pump. I connected it to the motor and found a few fuel leaks. In the next coming week I will be addressing those issues. I noticed I'm losing power in my turns now I think it's because I'm not getting enough fuel in the bowls or being able to keep it there. What is the correct way to set the floats?
 
Adding to my last post.... I fixed all the fuel leaks except one. I have 3 carbs when I pump the bulb fuel leaks from the top carb out the throat. I pinched off the fuel line to that carb and my fellow system holds pressure. Something tells me the top carb has a leak. Probably from a needle valve being misaligned with its seat.
The needles and seats are brand new. Hope this helps with any thoughts. I may have a float that is too low as well in that carb. I don't know ! Any help is much appreciated. Please review my last post as this one is a part B! Thanks
 
Fuel leaking out of the front of the carb is a needle/seat issue. With the bowls off of the carbs, turn the carb upside down and the float needs to be perfectly level with the base of the carb. Lever front-to-back and side-to-side. When you get the carbs back together, hook up a piece of fuel line and blow into it. With the carbs upside down, you should hear air flow. Slowly turn the carb upside down and you should hear the airflow stop. I may have already asked this, but when you disassemble carbs are you removing #4 and #5 and cleaning all the passages in there? Thats critical. Also, #45 is your high speed jet. When motors sit for a long period of time, they get a varnish like build up on them which makes the opening smaller. And, #39 is an important part too. You'll see all of these items on the link attached. Gas leaks must all be fixed. If gas can leak out when primer is pumped, then air can leak in when fuel pump is trying to pump gas to keep up with demand. The top carb leak and the fuel leaks might take care of all of your issues.
 
Thanks for all the good advise Oldsaltydog, I did not remove core plugs #4 and #5. I will this week. I did replace 1 one the high speed jets because the screw driver end was pretty stripped out. I'm ordering the other 2 this week. All #39 nozzle gaskets have been replaced. I did clean the jet orifices with a copper wire to make sure they are clean. When I reassemble the carbs I'll double check the floats as you suggested. That's sounds like a smart move. Should be back on the lake by the weekend. I'll repost my results.
 
Well I was able to get all the fuel leaks fixed, SO I HOUGHT! I had a float valve that had a bit of something down in the seat. Cleaned it out (top carb) cleaned everything with carb clean and compressed air. Put it back together and it appeared to hold pressure. I replaced the carb fuel lines with clear fuel line so I could monitor the fuel. Raced out to the lake to do a quick test before dark. Started up fine idle a bit high 1050 rpm, put in in gear, idle was a bit high under load 800 rpm. Took off, my vibration calmed down a bit and then WOT ran great for 30 seconds. Then the motor ran like it was trying to pop wheelies. Quik surges holding 25 to 29 mph. I squeezed the primer bulb and it was soft. Not holding prime. Why not? When I replaced all the fuel lines I reused the FDV and the primer bulb. I checked them and they appeared to be working properly so I didn't think twice about it. They are only one way valves so pretty basic, I thought! I think 1 of 3 things at this point can have slow leaks. Fdv may not hold over a period of time, same with the bulb, and the fuel pump is faulty. Probably should test the fuel pump but it is farely new. Any good tests for these fuel pumps? Please let me know if my thinking is incorrect.
 
Good to know Racerone.
So why am I not getting the fuel the motor needs? Weak pump? I had the system under pressure all night and the bulb stayed hard and the lines to the carbs are full of fuel and I don't see any leaks. I'll have those core plugs #4 and #5 in a day or so. Could those passages that were missed at cleaning be the problem? Is there a big difference in fuel pumps OEM vs aftermarket? I know the pump is new (6 months) but I wasn't the one that purchased it.
Thanks in advance!
 
What are the actual compression values tested today ?------Are you aware of issues with the exhaust manifold gaskets leaking on these motors?---Water can get into the cylinders.-------The motor is 50 years old and unless rebuilt there could be a number of issues besides carburetors.
 
All compression numbers were about 100 the last time I checked. I've tested with 3 compression testers and they are anywhere from 115 to 100 so I go with the lowest reading! Your right it did have a bad exhaust leak and I pulled the powerhead and resurfaced all the plates. I did the same to the head and head cover with new poppets springs and thermostat. I did not see any scoring or rust in the cylinder wall when I did all of that. I sea foamed the pistons while I had it all apart. I do not have a water leak anymore. The last time I checked the compression was after I completed the exhaust and head work, should have mentioned that first off.
New parts include:
Starter and solenoid
All coils and plugs
wiring from motor to battery, including battery
All fuel lines from tank to carbs, added an inline fuel filter
Top carb high speed jet
Fuel pump is pretty new, but not by me
water pump and all the rest that is required when servicing
and cleaned all the carbs minus the core plugs #4 and #5 passages, but I'll do them when the parts come in, I ordered the other 2 high speed jets and the new replacement idle RSTR jets as well. Those also will go in when I get my core plugs.
I pretty much have replace anything I've touched.
I wish I had raised the tank the last time I was out but I forgot to do it. Every time I've been out the motor has ran better and better. Just have to figure this out and she should be golden.
 
Racerone, The motor starts up very easily. It will die after a bit of running in gear at low idle too. When I look at the fuel lines to the carbs there isn't any gas in them, they are clear. So I pump the bulb until I see the fuel in the lines and the bulb gets hard and it will start up again.
 
Sorry I need to add... At WOT it wont die but it does surge. Rapid surge too a bit more than a second apart. Gets up to 5100 rpm 29 mph when it surges. It does have a bit of a shudder mid range as well.
 
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