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2 stroke bogging

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2strokebloke
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Joined: 03 Feb 2019
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PostPosted: 00:19 - 03 Feb 2019    Post subject: 2 stroke bogging Reply with quote

Hello all,
I have recently purchased a 50cc geared motorhispania ryz50 for just £100 , the bike was listed as unregistered and not working , I fully expected this bike to be a pain in the arse to get legal and running , long story short the “engine noises” as the bloke who I bought the bike off of ended up being a woodruff key £8 making a horrendous noise and preventing the starter motor from engaging. The Dvla gave me a runaround for around 2 months with registration until i bought a registered Peugeot XPS 50 frame (identical to motorhispania) and swapped the parts over.

This is where my issues began to arise , the bike starts instantly and idles perfectly on and off of choke , I have rebuilt the carburettor and cleaned everything with carb cleaner , blown out all fuel lines with a compressor as well as the fuel filler cap valve and have checked the vacuum fuel valve . I have also checked the spark plug and gapped it correctly as well as checking that the head bolts are all tight and that the exhaust has no blockages . Finally I will add that the fuel is fresh shell v power to eliminate that potential issue.

The actual problem with the bike is that it bogs under any sort of load , for example in neutral you can rev it up to 10,000 to 11,000 rpm no problem however as soon as it’s in first gear it won’t reach 4000 before bogging and dying . I have waited 20 mins before running attempts for the bike to warm up and it’s spitting out some oil from the exhaust and smoking correctly (eg a little but not excessively) does anyone have any ideas how I could fix this issue / what it could be caused by as I’m out of ideas

(This bike uses a water cooled minarelli am6 engine with oil injection)
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stinkwheel
Bovine Proctologist



Joined: 12 Jul 2004
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PostPosted: 01:09 - 03 Feb 2019    Post subject: Reply with quote

Couple of common stroker issues.

First and foremost. Fit a new plug if you haven't already.

Compression. Could it have a damaged bore/piston, broken piston rings?

Leaky crank seals.

Inlet air leak.

Does it have a standard air box, filter and exhaust?
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2strokebloke
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PostPosted: 14:14 - 03 Feb 2019    Post subject: Reply with quote

The bike has a standard air box and a new ngk spark plug though there is some flywheel play and regarding the exhaust there is a second pipe coming out vertical from the header end of the exhaust that a previous owner has plugged and jubilee clipped closed
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stinkwheel
Bovine Proctologist



Joined: 12 Jul 2004
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PostPosted: 14:22 - 03 Feb 2019    Post subject: Reply with quote

2strokebloke wrote:
The bike has a standard air box and a new ngk spark plug though there is some flywheel play


Play on the flywheel or play on the main bearings (usually presents as vertical play on the end of the crankshaft)? If the mains are shot, there's a good change the crank seals are too. Engine apart, new mains and crank seals.

Even if it's just the flywheel, there shouldn't be any play on it. I'm not familiar with your bike but they are usually on a keyed taper. If it's not totally solid on that, it will take out your woodroffe key then spin-up in short order. Your timing pickups will also be on there so if it's flapping about, you could be getting spurious signals.

If the taper is only a little damaged, you may be able to lap the flywheel back onto the taper with some fine grinding past but only do this if you are 100% confident you can remove all traces of the paste afterwards. I'd personally only consider attempting this without the crank on the bench on a bike with a "dry" alternator. The risk of grinding paste contaminating the oil is too great.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.
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2strokebloke
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PostPosted: 01:33 - 04 Feb 2019    Post subject: Reply with quote

I took your advice and checked the flywheel and crank end thoroughly, there is nothing wrong with the taper or the key , the issue is the crank moving with the flywheel and so I assume the bottom end bearings are blown , I have ordered replacements as well as seals , do you think this will solve the issue and if not what else should I check that I Haven’t allready
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Tankie
Trackday Trickster



Joined: 24 Feb 2017
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PostPosted: 06:56 - 04 Feb 2019    Post subject: Reply with quote

Blocked exhaust, decoke the system.
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stinkwheel
Bovine Proctologist



Joined: 12 Jul 2004
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PostPosted: 14:57 - 04 Feb 2019    Post subject: Reply with quote

2strokebloke wrote:
I took your advice and checked the flywheel and crank end thoroughly, there is nothing wrong with the taper or the key , the issue is the crank moving with the flywheel and so I assume the bottom end bearings are blown , I have ordered replacements as well as seals , do you think this will solve the issue and if not what else should I check that I Haven’t allready


Couldn't possibly say but if the mains are shot, they need replacing and there is a very good chance the seals will have gone at the same time. It'll never run properly with leaking crank seals.

Yopu'll have a good oppertunity to scrutinise the rest of the engine for issues while you're in there.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.
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Tankie
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Joined: 24 Feb 2017
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PostPosted: 15:38 - 04 Feb 2019    Post subject: Reply with quote

Leaking crank seals normally give very poor starting
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2strokebloke
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PostPosted: 13:28 - 17 Feb 2019    Post subject: Reply with quote

Just an update , so I have checked thoroughly the crank seals , put a new gasket set on the cylinder and head , equally I have changed the previously incorrect spark plug and replaced the old fuel tap for an identical new one , I have also pulled the flywheel and checked the stator , to find a broken stator backplate (mount for stator) that I have replaced , however I am still plagued with this same issue of bogging under load , does anyone have any further ideas ,
I have also today taken off and apart the carb that came on the bike , it is bigger than stock , stock is a dellorto phbn 16mm and this bike has a phnb 19mm with a large main jet (84) and a larger than useual Idle jet (45) would this cause concern or shed any light to my problem , also the spark plug is allways wet and slightly black when pulled , and the air filter Is stock
Thanks
2strokebloke
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Tankie
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PostPosted: 16:40 - 17 Feb 2019    Post subject: Reply with quote

Either replace the exhaust or clean it out,
I use an oxy acetylene flame carefully to set fire to the carbon then turn off the acetylene and keep it burning on the oxo
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2strokebloke
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PostPosted: 22:17 - 17 Feb 2019    Post subject: Reply with quote

Is it definitely the exhaust or could it be another factor like cdi or some other obscure part , and I don’t have a oxy torch so how else would I clean the exhaust?
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Tankie
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PostPosted: 23:08 - 17 Feb 2019    Post subject: Reply with quote

The old chemical way was to use caustic soda . The burning method is better , maybe a gas torch and a compressed air line
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2strokebloke
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PostPosted: 23:27 - 20 Feb 2019    Post subject: Fixed Reply with quote

Just an update , I have fixed the bike , I took the advice to clean the exhaust with no luck and then after checking the cdi came to the conclusion that it was fine , it then dawned on me that the bike had a brand new ( and unfortunately cheap ) cylinder kit fitted , this lead me to believe that , due to the larger than stock carburettor, the bike has previously had a 70cc kit fitted , and judging by the shitty quality of Previous repairs (rounded bolts and dry joints etc) the 70cc kit blew up , this led me to the conclusion that the carb had been butchered and fucked about with no end as well , so I went on eBay and for £15 bought a used carburettor off of an updated model of my bike , though this was stock of course, my bike 2005 carburettor 2011 , I rebuilt and cleaned the carburettor before fitment and sure enough the bike works perfectly albeit running a little bit rich , I would implore anyone with seemingly unfixable fueling issues like I had to buy a secondhand carburettor off of a WORKING model of your bike , this is because the carburettor is known to have been working at some point and so provides a baseline ,
Thank you all for all of your prompt and very helpful reply’s
2strokebloke
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Tankie
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PostPosted: 07:56 - 21 Feb 2019    Post subject: Reply with quote

At the start of this thread you stated you had rebuilt the carb.
How did you rebuild the carb?
Pattern carb rebuild kits have inferior fuel metering components in them and normally don't include the items you really need which are jet needles and needle jets, these items are hard to find or unavailable, these are the most important items to ensure the carburetor performs correctly .
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St George
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Joined: 19 Feb 2019
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PostPosted: 18:11 - 13 Mar 2019    Post subject: Reply with quote

Having just read the thread, I would have said too rich at the outset, like driving with the choke out.
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2strokebloke
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PostPosted: 23:17 - 10 Apr 2019    Post subject: Reply with quote

In answer to tankie and st George , by rebuilt the carburettor I did not mean refurbish , this was intended to mean that I took apart the carburettor and sprayed everything down with fresh petrol and carburettor cleaner , also these am6 engine 50cc geared bikes all come with dellorto carburettors and so the refurbishment kits are all quite good (bar the Chinese ones) and parts , jets etc are easy to come by. And st George you were right , the bike would appear to have been fitted in its past life with some sort of performance kit (70cc) and has all of the signs of an engine Grenade , this is because carburettor was a 21mm dellorto rather than the stock 17.5mm , the fix was surprisingly simple , these bikes being a favourite of 16 and 17 year olds such as myself they’re crashed all the time , this meant that for a whoppping £15 shipped I got a stock carb off of a running (although mangled) bike so the excessive rich condition was fixed
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Tankie
Trackday Trickster



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PostPosted: 05:31 - 11 Apr 2019    Post subject: Reply with quote

Nice one
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St George
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PostPosted: 12:37 - 11 Apr 2019    Post subject: Reply with quote

Glad I was right for a change, pleased for you.
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