# YS828T engine rpm problems



## grat_master (2 mo ago)

Hi,
I bought a Yamaha YS828T 7KF2 but I am having troubles getting the engine to run good. It won't run at idle and when max throttle it's always hunting for rpm, up down up down constantly. I can also hear some small backfires.

I changed the oil, changed the spark plug, cleaned the fuel filter, cleaned the air intake box, put fresh fuel in it, tried to adjust idle screw and jet pilot (?) screw on the side of carburator. I also removed the carb, removed the main jet and side jet and everything looked clean. I still sprayed some brake cleaner in there. Both gaskets are still there but they look really dry.

When running at full throttle the arm going to carburator throttle always moves and this makes the rpm go up and down.

Anyone can help me out please? I don't have much knowledge of small engines but if I can learn I'll be able to fix it. 
Thanks!


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## leonz (Dec 12, 2014)

Did you check for dirt, gum and or varnish deposits in the gas tank? 
If the fuel line is rubber it may be collapsing.


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## grat_master (2 mo ago)

leonz said:


> Did you check for dirt, gum and or varnish deposits in the gas tank?
> If the fuel line is rubber it may be collapsing.


No I did not check the gaz tank. Now it's full of fuel, will be a pain to empty it. There wasn't much dirt on the little filter over the small reservoir on the right side, same thing for the fuel bowl. Not much dirt anywhere actually.

I removed the cover over the choke handle and ran it like that so I can adjust and monitor. I didn't see fuel hose collapsing.


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## cpchriste (Jan 19, 2014)

First, pull the pilot jet tube (~3" long) and make very sure every orifice is clean.
Second, if that doesnt work then you may need to pull the expansion plugs in the carb and get any debris inside out of there.
I think step one will resolve your problem if you're thorough. 
I'm assuming you did clean the main jet nozzle too.


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## grat_master (2 mo ago)

cpchriste said:


> First, pull the pilot jet tube (~3" long) and make very sure every orifice is clean.
> Second, if that doesnt work then you may need to pull the expansion plugs in the carb and get any debris inside out of there.
> I think step one will resolve your problem if you're thorough.
> I'm assuming you did clean the main jet nozzle too.


If you refer to the image, it would be part # 9 right? If yes, I did not remove that.

What is expension plug you are talking about?

What I did is remove the carb from the machine, remove the bowl, clean the bowl, removed part # 10 from diagram then shoot brake cleaner in there (I noticed no obstruction), removed part # 6 from diagram then shoot brake cleaner in there (I noticed no obstruction), reassemble everything back together. Nothing was dirty anywhere. I did notice a hair line crack on one of the tab holding the needle holding the float but I don't think this matters because the float moves freely.

Thanks for your help.


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## cpchriste (Jan 19, 2014)

Yes, pilot jet is #9.
Welch plug is another name for what I called an expansion plug.
It would be good to also make sure #11 orifices are clear.
Again, I think your problem is in #9


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## grat_master (2 mo ago)

Alright I got back in the garage and removed #9 and #11. Both were clean at first sight. I still cleaned them. I used a single small wire from a 12v wire to clean the small orifices.

I didnt put anything back together yet as tomorrow I will try to source the gaskets between carburator and plastic intake manifold and cylinder head.

Everything in the carb looked clean. Maybe it's leaking? I noticed the spark plug was really black which means it is running rich. I didn't remove the new spark plug tho. I'll check that tomorrow. I used the snowblower today to remove the 15cm or so snow in the driveway.


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## grat_master (2 mo ago)

I tested the float. I brought the carb inside the house, put it upside down and filled the rubber hose still attached with water. Water stayed in the hose but as soon as I opened the float, water was sucked in. I think this confirms the float is not leaking.

Next I removed the new spark plug. It was really light color, looks like it's starving for fuel, from my experience reading spark plugs. I also tested the engine compression. First crank it went right up to 60-65 for each 3 tests I did then with 2 more cranks it went up to 92. I think this is a healthy engine.

So now everything is clean, engine compression is good, float does not leak, general condition is top notch. All is top notch except the gaskets. I ordered them and will have them next week. I hope this fixes my problem.

Any other suggestions while everything is tore down?


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## grat_master (2 mo ago)

Anyone knows how to adjust governor on theses engines?


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## tabora (Mar 1, 2017)

grat_master said:


> Anyone knows how to adjust governor on theses engines?


Join the Yamaha Facebook Group. I understand that they have the service manuals available.








Yamaha Snow Blowers - old & new | Facebook


This group was generated due to the fact that the "fan club" page is infrequently viewed. Since parts & technical service are hard to obtain, this site should prove beneficial. These units were 1st...




www.facebook.com


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## cpchriste (Jan 19, 2014)

grat_master said:


> Anyone knows how to adjust governor on theses engines?


If you're asking how to adjust max RPM, there's a stop screw in the linkage under the carb that does that.


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## grat_master (2 mo ago)

cpchriste said:


> If you're asking how to adjust max RPM, there's a stop screw in the linkage under the carb that does that.


No I was talking about the Governor. I found it in the service manual but was never able to do what it says. 

Anyway, you were right from the beginning. My problem was in #9 jet. I cleaned it 4-5 times more and dirt came out. Now the engine idles fine. I need to buy a rpm induction gauge to adjust the min and max rpm as they are out of spec. I'm also waiting on new carburetor gaskets so I'll do everything at once. 

I also adjusted the skid shoes and scraper plate. All it's missing now is to change oil in the diff but I have too much fuel in the tank to put the machine in a vertical position. I'll do another oil change because the oil is extremely dark after only one use.

Thank you for your help.


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## grat_master (2 mo ago)

Well, still not good.

The machine now starts correctly and idles correctly. My problem is with max rpm. Even with the throttle scew scewed in to the max, rpm are over 4200 at half throttle and the scew is not even touching the stopper yet. I didnt try it but I'm sure it'll go over 5000rpm at max throttle which is way too much.

While cleaning the jets I saw micro fissures in the pilot jet. While blowing through the tiny top hole and closing the bottom 2 bigger holes I can feel air coming out through the fissures. Could this cause a problem?

I'm also not able to adjust the governor as per the manual. In it, it says to loosen the nut, turn the arm counter clock wise until it stops then turn the governor screw with a flathead screwdriver counter clock wise until it stops then retighten the nut. I can not move the governor screw in either directions. I can't see anything more on that in the manuals.

Any help?

edit : 

The governor shaft only moves about 2mm in either direction. Is this enough?

I managed to get the max rpm at the correct speed. It was the governor arm nut that was loose. But now my problem is the throttle won't stay at max rpm. I adjusted it to 3830 but as soon as I remove my hand from the throttle arm, it goes down to 2950. I don't know why. Any clues?


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## cpchriste (Jan 19, 2014)

grat_master said:


> The machine now starts correctly and idles correctly. My problem is with max rpm. Even with the throttle scew scewed in to the max, rpm are over 4200 at half throttle and the scew is not even touching the stopper yet. I didnt try it but I'm sure it'll go over 5000rpm at max throttle which is way too much.
> 
> While cleaning the jets I saw micro fissures in the pilot jet. While blowing through the tiny top hole and closing the bottom 2 bigger holes I can feel air coming out through the fissures. Could this cause a problem?
> _*I don't have a clear mental picture of the fissures. Still, I don't think they could cause this problem, especially since it idles well. I would buy and install a replacement jet for peace of mind.*_
> ...


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## tadawson (Jan 3, 2018)

What throttle arm are you holding? The one from the gov? If so, you set it wrong . . . If an arm from the end user throttle control, then it is likely slipping. The goal in setting thengov is tomset the _governed_ speed, not maximum, since the gov _must_ be able to apply additional throttle to compensate for load.


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## grat_master (2 mo ago)

I'll upload pictures tomorrow.

I hope I don't have to go inside the front cover to check the governor shaft. 

Speaking of which, is it normal that it moves in and out of the engine? So to sum it up, cw or anti cw it moves only like 2mm but in and out it moves more like 5-7mm.

I also tested the gaskets and it seems they leaking as when I spray brake cleaner around them the engine sputters a bit. I got my new gaskets I'll install them tomorrow. I'll take pictures at the same time to explain everything.


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## grat_master (2 mo ago)

tadawson said:


> What throttle arm are you holding? The one from the gov? If so, you set it wrong . . . If an arm from the end user throttle control, then it is likely slipping. The goal in setting thengov is tomset the _governed_ speed, not maximum, since the gov _must_ be able to apply additional throttle to compensate for load.


I'm talking about the throttle arm to control the engine rpm. The one designed for that. That arm is moving on a pivot point, push/pull ing on a metal rod that moves another pivot point. That second pivot has the bolt to adjust max rpm. It then goes to the governor arm by a spring, then the governor arm is secured on the governor shaft then on top it moves the throttle on the carb. 

I adjusted everything as per the manual.

Like I said earlier I'll try with new gaskets and take pictures at the same time.


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## tadawson (Jan 3, 2018)

grat_master said:


> I'm talking about the throttle arm to control the engine rpm. The one designed for that. That arm is moving on a pivot point, push/pull ing on a metal rod that moves another pivot point. That second pivot has the bolt to adjust max rpm. It then goes to the governor arm by a spring, then the governor arm is secured on the governor shaft then on top it moves the throttle on the carb.
> 
> I adjusted everything as per the manual.
> 
> Like I said earlier I'll try with new gaskets and take pictures at the same time.


OK, thanks for the clarification. Your pictures never showed the other parts, so I was unclear.


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## grat_master (2 mo ago)

Alright, here are the photos. I went ahead and removed the engine to check for the governor. 2 small weights were over the collar so I replaced them correctly. Unfortunately, engine does the same thing. It always slowly goes down to idle rpm as soon as I remove my hand from the throttle handle. Please help.


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## cpchriste (Jan 19, 2014)

I'm having trouble understanding the current state of affairs in your repair. I'm going to take a wild guess that your current situation is related to the throttle control slipping instead of sticking in place. There are wave washers in that pivot assembly as well as a locknut that can be tightened on the pivot. Either of these items can deteriorate and allow the throttle control lever to move by itself. There have been postings about this issue in Yamahas and I've experienced the issue several times.


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## grat_master (2 mo ago)

cpchriste said:


> I'm having trouble understanding the current state of affairs in your repair. I'm going to take a wild guess that your current situation is related to the throttle control slipping instead of sticking in place. There are wave washers in that pivot assembly as well as a locknut that can be tightened on the pivot. Either of these items can deteriorate and allow the throttle control lever to move by itself. There have been postings about this issue in Yamahas and I've experienced the issue several times.


which pivot are you talking about? As soon as I remove my hand from the throttle everything goes back to idle : throttle handle, spring, pivot, governor shaft, governor arm, carburator. Everything is as tight as it can be.

Also what is hard to understand in this situation? I can provide more details if it's needed.

Here is what I did :

clean carburator inside out + all jets -> this corrected the start up and idle
adjusted the governor
removed the engine and verify governor inside the crank case -> 2 small weights on the 9 total were not correct so I reinstalled correctly, also fixed the over vibration of engine
reinstalled everything as per the service manual
fresh oil, fresh fuel


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## leonz (Dec 12, 2014)

The wave washer is compression washer that loses tension over time.


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## grat_master (2 mo ago)

leonz said:


> The wave washer is compression washer that loses tension over time.


Which wave washer? Can you show on a picture?

I found it on impex. I looked at my throttle arm and I don't have one. I will try to source the corrects parts for the throttle arm now. I'm pretty sure my problem is related somehow because even if I adjust the max rpm to around 3k rpm it still decreases by itself. The arm always goes back to the same position, almost at the lowest point.

Thanks for pointing this to my attention!

Edit : I tightened up the pivot screw and it worked. RPMs now stays steady. By looking at parts diagram on impex I found out I have a mix match between ys624 and ys828 parts for the throttle arm. For now it looks like it's working anyway so I'll leave it like that. It's super late right now so I only did a quick test. Tomorrow I'll readjust idle and max rpm and I should be good to go. I'll report back.

For now, many thanks to you and cpchriste. You guys helped me out a lot, I really appreciate.


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## grat_master (2 mo ago)

I think this is finally a case closed! Idle is steady around 2200rpm and max throttle is steady around 3810rpm. Engine been running for around 1 hour on the new oil after I opened the crankcase and drained all the black oil and it is still like new so that's even better news! Throttle is not moving anymore but is harder now to move but I don't care, as long as the engine stays steady that's all that counts.

Thanks all for your help! I was at lost but you all gave me great tips and I managed to get it to top shape. I'll keep up on the maintenance and adjustments so that snowblower lasts me many many years.


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## JapDolls (4 mo ago)

cpchriste and others were correct in identifying root cause of your throttle problem. When you get your hands on a wave washer , it should be installed next to the throttle handle shaft, then followed by the two 10mm nuts. Adjust the first nut so that throttle handle stays at maximum position without moving off that position , then tighten lock nut. Start engine and move handle to max and check if it stays in max position. When tension is adjusted correctly, you should feel a light drag on the throttle handle when its being moved from idle to max and vice versa. The handle should stay in any position between these two extremes. I have found best time to adjust the tension was during snow removal when all the moving parts ( auger, impeller, transmission and engine ) and their vibrations would indicate if the adjustment made was adequate. BTW, if you cannot get a wave washer, try a split washer ( after bending the two ends closer together first ) in its place. I have also used an elastic band looped around the throttle handle to the choke lever to maintain full throttle in a pinch. Good luck and happy snowblowing.


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## grat_master (2 mo ago)

JapDolls said:


> cpchriste and others were correct in identifying root cause of your throttle problem. When you get your hands on a wave washer , it should be installed next to the throttle handle shaft, then followed by the two 10mm nuts. Adjust the first nut so that throttle handle stays at maximum position without moving off that position , then tighten lock nut. Start engine and move handle to max and check if it stays in max position. When tension is adjusted correctly, you should feel a light drag on the throttle handle when its being moved from idle to max and vice versa. The handle should stay in any position between these two extremes. I have found best time to adjust the tension was during snow removal when all the moving parts ( auger, impeller, transmission and engine ) and their vibrations would indicate if the adjustment made was adequate. BTW, if you cannot get a wave washer, try a split washer ( after bending the two ends closer together first ) in its place. I have also used an elastic band looped around the throttle handle to the choke lever to maintain full throttle in a pinch. Good luck and happy snowblowing.


Thanks for all information! 

I don't have any of those washers and nuts. I have the 828 bracket and handle but everything else is 624. I'll try to source the correct parts and adjust it accordingly but at least for now it works good. I tried at full throttle + drive + auger and it stayed at the required rpm. Will see if it loosen later during the winter. Will probably be a challenge to source all the parts so I hope it stays good.


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