Mr1 tech help!

[jman45489]

So im at a loss i rebuilt my starboard engine this summer and have nothing but issues since than. It is an 08 ar210. I cant tell if i have a knock or just a missfire. I do have a video i can share of it if needed just not sure how to share on the forum as it says the file is to large. So heres some back ground. Im not an engine builder but i am a b tech in a repair shop and have built a handful single cylinder engines. When i first started this project it was due to burning about a quart of pil everytime we took it out last year. (First year owning this boat) we never had runability issues just if i didnt watch it. It would throw the low oil light which after the first time i always made sure i had checked it after warm up and carried an extra quart on board. So during the disassembly i found cylinder 1 full of scoring and rings out of spec. So i sent the block to mellinium with 4 yamaha piston and ring sets amd had them sleeve the engine and set the ring gaps. During reassembly i did use the same rods and bearings as they looked in good shape and didnt previously have any issuses. While building it i also replaced 5 valves in the bad cylinder and the timing chain.I put it in and when i fired it up! It was tough to start and when it did it would run for 3 seconds or so and die. After a few attempts (i had assumed it was just from sitting) it idled but had the knock like in the video. I decided the noise sounded like it was coming from the back lower part of the engine. We pulled the engine back out and found i made the mistake of putting a chain tensioner in backwards. I have no idea how i made the mistake i assume just pushing to put it together and lost focus. So i ordered a timing set from sbt and put that in and tried to run it again. Still the same noise. So i pull the engine and have my brother in law come help me tear it down again looking for issues. He is a more knowledgeable auto tech but still not an engine builder. We find that for some reason number 2 connecting rod doesnt spin as free as the others. So i ordered a new rod from sbt and all new big end bearings. We plasti guage them amd all come in to spec according to the manual i have. He stays and we rebuild the darn thing page by page in the manual watching for other mistakes i may have made. We put it in the boat and it still has this damn noise. It comes from the lower case half/ crank area. From the best i can tell the oild pump seems fine the gear for the timing chain didnt apear to be damaged and the engine was still in time last time we tore it down. I didnt think to check it the first time. I also have an ebay version of the yamaha diagnostics and trying for a cylinder drop test doesnt prove any one cylinder does or doesnt make a difference. I also dont recall the program showing missfires like my scanner at work. I pray someone has the solution before my wife looses her patience and i have to sell the dam thing. The kids love it as much as me but bust out another thousand on this project has been an understatement. Thanks for any help you may have to offer!

 

[Dixemon]

If i might ask how many hours you had on the motor? Ill second guess your build for you.
1. Are you absolutely sure that you timing is correct between your crank and cams. It only takes being 1 tooth off to have major problems.
2. Are your valves set correctly
3. Are your coil cables in the right order

 

[jman45489]

Awesome thanks for your interest! The manual only showed timing the crank with a dial bore guage so i did buy a harborfreight one, but i had to use a 6 inch extension to get it on top of the piston so there could have been a slight variance in measurement there.
2 unless the new valves i put in have settled im pretty confident in they are shimmed to spec. In the dirtbike engines i have never seen it happen with out multiple hours on the build.
3 The plugs for the coils lay in order in the harness and are pretty short so im confident they arent out of order

Ill try to verify the timing in the boat again tomorrow.

 

[jman45489]

August 28, 2022

youtube.com

 

[CaptRedbeard]

If i might ask how many hours you had on the motor? Ill second guess your build for you.
1. Are you absolutely sure that you timing is correct between your crank and cams. It only takes being 1 tooth off to have major problems.
2. Are your valves set correctly
3. Are your coil cables in the right order

I’d second the timing question. It took me a while to figure out the timing on the mr1. Cyl 1 is nearest the magneto and the camshaft lobes will point away from each other at tdc compression.

Have you done a compression test?

 

[Bruce]

Being an AR210 the engine is not an HO.

Is there any possibility that you used any HO parts? A 2007+ 230 would have HO engines.

If you do not find the problem before I suggest that you replace the SBT parts to see if they may be the problem.

 

[jman45489]

Thanks for suggestions i will double check timing again weather permitting this evening. I have not done a compression test but will do that also this evening. And i did question the rods from sbt as they had bolts holding the caps together and not studs with nuts like the oem rods but called sbt to verify it and they informed me they where updated rods...

 

[jman45489]

Thanks for the help guys! Ended up finding cylinder 3 and 4 exhaust valves where tight, about .10mm instead of .25mm thanks again for all your suggestions hopefully we can have an uneventful weekend on the water!